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Fish Fertilizer – Is it Worth Buying?

Fish fertilizer is very popular. It is reported to be a good source of nutrients and a good source of proteins, amino acids and oils – for your plants. Can plants use fish proteins and oils? Is fish fertilizer a good source of nutrients?

Before I go any further let me say that there is nothing wrong with using fish fertilizer. It will help make your plants grow. I have two problems with fish fertilizer; it is extremely expensive compared to other sources of fertilizer and many of the claims for it have no basis.

making fish fertilizer

Making fish fertilizer

Fish Emulsion vs Fish Hydrolysate

What is the difference between fish emulsion and fish hydrolysate? The difference from a plants point of view is minor, but if you are trying to sell product–there are big differences.

Fish emulsion and fish hydrolysate start with the left over bits from the fish industry–the parts no one else wants. These are then treated with various chemicals and enzymes to break down larger organic molecules into nutrients and other small organic molecules. Further treatment can take one of two paths; it is either heated or cold processed. Fish emulsion is the end product if the heating process is used. Fish hydrolysate is the result of using cold processing.

There is great debate between the benefits of emulsion vs hydrolysate–which is better? The reality is that plants can’t use most of the large or even small organic molecules from either process. Normally microbes in the soil degrade these to nutrients plants can use. So the argument that heat in the emulsion process is detrimental, makes no sense. it is true that heat will denature proteins, but they need to be denatured for the plants to use them.

I think the arguments for or against either process is just marketing hype. I have seen no scientific evidence to support the superiority of either process.

Fish Fertilizer Benefits

Fish fertilizer is an organic product–for the most part. So it does have the benefits other organic soil additives have. It feeds plants, microbes and improves soil structure.

But proponents of fish fertilizer make claims that do not apply to other organic fertilizers. Most seem to be centered around the fact that the liquid fertilizer contains proteins and oils. We all know fish oils are very important for our health and so they must be good for plants, right? Wrong!

Plants can’t make use of large molecules such as oils and proteins; see Organic Fertilizer – What is it’s Real Value? for more details. When these molecules are added to soil, microbes digest them and turn them into small molecules like nitrate, and phosphate. It is only then that plants can make use of these molecules.

Since the large molecules need to be degraded before plants can use them, there is little difference – to the plant – between proteins and oils from fish, cows (manure), or even plants. I have found no support for the claim that fish fertilizer is better than any other organic fertilizer.

The main thing plants need from fertilizer is a source of nitrogen. Garden soils usually have enough P and K and the other minor nutrients. Nitrogen is the thing that is missing in soils. Given this fact, fish fertilizer is no better or worse than other types of fertilizer.

Fish fertilizer has about 2% nitrogen, which is the same as most organic fertilizers; compost, manure, and coffee grounds.

Is Fish Fertilizer Organic?

This probably seems like a dumb question–fish are organic so why would fish extracts not be organic? Here’s why. In the process of turning fish scraps into fertilizer companies add a number of chemicals, including phosphoric acid, and odor inhibitors. Apparently, as long as these ingredients form less than 1% of the finished product, the product can still be called organic. Who knew–organic fertilizer only needs to be 99% organic!

Cost of Nitrogen

I checked several fish fertilizers and a common analysis is 2-4-2 and if you buy in large containers you can get 9 lb (3.8 Kg) for $25. Small quantities are even more expensive. This fertilizer has 2% nitrogen, and so the cost for the nitrogen is $33 for 100 g of nitrogen. Wow! Even fresh caught Atlantic salmon doesn’t cost that much!!

What is the cost of 100 g of nitrogen if you buy a commercial fertilizer? Scotts sells a 30-0-9 at $17 for 6.2 Kg, or $0.91 for 100 g.

Fish fertilizer is 35 times more expensive than commercial fertilizer and plants can’t tell the difference between the two sources of nitrogen.

I can hear your objection – BUT … fish fertilizer is organic. That is true, and organic fertilizers do more than just provide nutrients. They also help build better soil by feeding microbes. Fish fertilizer is about 14% protein which is the same as manure. A 30 lb bag of manure will cost you $4 compared to $75 for the same amount of fish protein. Manure bought in bulk is even cheaper.

I really can’t think of any good reason to buy fish fertilizer if other sources of fertilizer are available.


1) Photo Source: Cheryl’s Garden Goodies

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Robert Pavlis
Editor of
I live in southern Ontario, Canada, zone 5 and have been gardening a long time. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

I hope you find Garden Myths an educational site that helps you understand your garden better.

143 Responses to 'Fish Fertilizer – Is it Worth Buying?'

  1. Nigel says:

    Hi Robert, Thanks for the interesting and thought provoking read. I guess my response to your well titled article was: “Is any fertiliser/input worth buying?” As I am sure you know, throughout the world there are different forms of low to zero input farming models proving to be effective. I’m really interested in applying that philosophy to a small suburban garden. I do make FAA and, as others have suggested, I try to harvest pest species. Many of the low/zero-budget farmers harvest fish from their own stocked dams. Both methods make it essentially free and sustainable. Which brings me back to my expansion of your question. Is it worth buying ANY gardening/farming input? I really don’t think so. Commercial gardening products are insanely expensive for home use. I am learning that there are viable alternatives that I can produce for zero to minimal expense. These days no kitchen or garden waste ever leaves my home and I even collect some from neighbours and friends. Sometimes I even forage for other supplies like nettles (which are an invasive species in my country). I convert these ingredients into a range of different products from compost and bio-char to fermented solutions and tinctures that support soil and plant health and deter pests and disease. So I think you are right. It’s not worth buying fish fertiliser. It’s not worth buying any gardening inputs – particularly chemical based ones. We can make what we need cheaply, ethically, and sustainable ourselves. 🙂

    • I agree that for home use you probably don’t need to buy any fertilizer. For farms it is worth buying fertilizer or they would not do it.

      Most homeowners use way too much fertilizer, which not only costs a lot, but makes a lot of pollution.

  2. Robert, thanks for your simple explanation of the difference between emulsion vs hydrolysate. One aspect that I wanted to comment on is that myself and others have seen a big difference in microbial growth when using hydrolysate over emulsion.

    Under a microscope, it’s pretty easy to test the two types and see what microorganisms are grown out. Fish hydrolysate has been proven to be a good bacterial and fungal food (Keep in mind I’m generalizing across brands here). Fish emulsion…..well not so much.

  3. I believe fish, seabird guano and kelp products add micro nutrients and trace minerals in an ideal balance. All life evolved from the sea. The sea contains mineral balances most ideal for the building blocks off life. Inland soils vary quite a bit in composition and most of them have imbalances of one sort or another. They imbalances are mostly micro nutrient in nature and are improved by using sea sourced fertilizers. I am a long time market farmer and I get better yields and higher quality produce than my farm neighbors by using sea based fertilizers.

    • Re: “All life evolved from the sea. The sea contains mineral balances most ideal for the building blocks off life”. The problem with this concept is that many organisms that live on land have developed genetically for a long time. As part of that development they have changed their requirements for the nutrients they need.

      I am quite sure that even the organisms living in the sea do not all have the same requirements for this special balanced nutrient mixture.

      • Thanks for responding Robert. I live in the rich farming Willamette Valley in Oregon. I raise sheep and I know a lot of other sheep breeders. Why do we have to supplement our sheep with salt and Iodine? If as you say organisms have evolved to not require nutrients mostly found in the sea. It has also become common practice to feed our sheep kelp meal supplements as sheep farmers all over the country have recorded increased growth and health when adding kelp-meal to feed.

        • I did not say “organisms have evolved to not require nutrients mostly found in the sea”. They evolved to use a different ratio of these nutrients. So that the sea may or may not provide the right ratio.

          Sheep may do well with added kelp to their diet, but kelp is a plant, and all plants contains thousands of chemicals. I doubt anyone knows which of these chemicals are helping the sheep.

          • Well we do know that whatever in the kelp is helping the sheep is adding something that is not found in Willamette valley soil pasture. In my trials growing fruits and vegetables for market I have noticed the same thing. Marine based fertilizers Kelp/fish add something that land based chicken/cow organic fertilizers are not. The performance is better in Willamette valley soils.

  4. Glyn Attwood says:

    I occasionally use liquid fish fertilizer but was wondering about the mercury content. Does it get destroyed in the heating process?.

  5. Robert Long says:

    Interesting article Robert and a needed perspective. I have noticed that when I use fish emulsion fertilizer, I often see a brighter, more yellow-green flush to especially new growth than with other fertilizers. i have also noticed that my plants seem less apt to show effects of over-fertilization when I have accidentally done so. Do you know of any reason why fish fertilizer would seem to have this “buffering” effect to nutrient levels? Or am I simply suffering the effects of anecdotal evidence?

    • One reason you are less likely to over fertilize is that fish fertilizer contains low levels of nutrients. Using more dilute solutions makes it easier not to add too much. But then you can dilute any soluble fertilizer to get the same benefit.

    • If you want to know the real benefits of the various fish products, type into your browser “the benefits of fish liquids in agriculture” Nutri tech solutions and organic farming systems have some positive blurb on these and other products, kelp, molasses and humates.
      Fish liquids will out perform urea when used over time

      • If this company is promoting the benefits of things like “kelp, molasses and humates”, then clearly their material can’t be trusted as being fact.

        Re: “Fish liquids will out perform urea when used over time” – that may be true. Urea is just a nitrogen source, and fish liquids contain other nutrients as well, but it is only true if the soil is missing these other nutrients.

  6. Maikl says:

    Do fish fertilizer, it is not advantageous in that it contains an amino acid?
    Commercial fertilizers with amino acids are expensive… As for nitrogen fertilizers Robert is right…

    • There is little evidence that amino acids are of any extra value – other than a source of nitrogen.

      • Ray Roberts says:

        Well, amino acids do have extra value, they are composed of nitrogen, carbon, and oxygen in some. Microbes use them,for the N and H mainly, critical elements to build other metabolites.
        Amino acids are small enough, they can pass though cell walls. Some are excellent chelators of secondary and micronutrients. For example two glycine molecules can attach between them a calcium ion. There are commercial amino-chelated fertilizers that use this strategy. Plants can absorb these amino chelates directly through roots or foliage.
        Mycorrhizal fungi have been shown to deliver amino acids directly into the roots.
        Of course the amino acid glycine is used in another way for a more destructive purpose to plants, making the herbicide Glyphosate (N-(phosphonomethyl)glycine) .

  7. robert moorman says:

    Try to use blue green algae from pond water lakes and streams . Seem to me that it would be a better fertilizer than most .

  8. john Murtaugh says:

    I have been very interested in everything posted in this discussion and thought it would be helpful to respond to the latest post by reference to which discusses how salmon help the forest in British Columbia.

    Thanks for the great website!

  9. Gardner Wolfe says:

    I light of all that I have read, I am still in a quandry as to what a real fertilizer is. Culture recommendation for my Violette De Bordeaux Fig call for the use of 10-10-10. What would you suggest?

  10. Mike says:

    So what would you suggest as a good alternative? In Canada, we definitely get the short end of the stick when it comes to variety of goods available as well as reasonably priced. Most of the equivalent stuff in the US is half of what it costs here, even before the poor dollar conversion currently but shipping something heavy negates all the savings. I’m only a small time gardener.

  11. It’s surprising the article makes no mention of the full spectrum of minerals present in sea food, and therefore the fertiliser. Sea water is known to have an astounding 82 elements (don’t have the link, please Google it). The only thing that prevents us from using sea water as fertiliser is the high sodium content. Fish do the wonderful job of filtering out that excess sodium and leaving you with extremely mineral rich organic matter !

    BTW, if you guys are sold on fish, you really should be doing FAA … Fish amino acid … A concoction recommended by Korean natural farming. This process will break down most of the larger molecules and also multiply the microbial count before you apply all that yummy fertiliser to the soil.

    • Wow – 82 elements. So what. How many of these are needed by plants? I tell people plants use about 30 nutrients and that number is higher than most references.

      How many of the 30 nutrients are missing from soil? Most are rarely deficient in garden soil.

      Adding 82 elements to soil serves no benefit to plants or soil organisms.

    • I have Googled it. Sea water contains “47 minerals and metals” according to Stanford University. And plants use at most 24 elements. See my new post Trace Mineral Fertilizers – How Many Nutrients Do Plants Need?

      • Nick Follett says:

        It couldn’t possibly have 82 elements in – element 82 is lead, most people consider this the heaviest non-radioactive element (or perhaps 83, bismuth). So you’d have to have everything, including the noble gases, silicon, gold etc., to even reach that number!

        I suspect the choice of the number 82 isn’t a coincidence, but probably the collision point of various half-read and half-remembered ‘facts’ by someone at some point down the line.

  12. Daniel Hand says:

    Robert Pavlis, I just finished reading this article/thread and I found it very helpful. I appriciate how you explained some of the commonly accepted false ideas that have become so become so popular in many organic gardening circles.

    I look forward to reading more of your work in the future!

  13. Ari says:

    Native Americans would start off their “3 sisters” gardens by burying fish. Then they planted nitrogen fixing legumes, along with corn and squash. They didn’t need to keep adding fish to their soil afterwards

    • Ken Parker says:

      I am not in agreement on this folklore and there is no documented proof to generalize that native Americans used fish as part of their agricultural approach to growing corn. Maize is widespread across North America and Mexico. How does this explain the tribes of the southwest: Navajo-Blue Corn, Hopi who also grew several varieties of corn & beans. I am a grower of indigenous corn myself. Corn is relayed to grass and both are heavy feeders of nitrogen. I certainly accept the permaculture approach of the three sisters method and it all makes scientific sense.

      • Shannon says:

        There is a lot of romantic sales pitches around based on the native Americans planting fish under there corn. In actual fact recorded litriture shows that fish were used in the U.K first and it was a tribal elder from, I forget the area now but he was kidnapped in early settlement of the US and taken to England, “educated” and he learnt from locals who used fish in gardening there. After two years he returned to his native homelands and vwollar, the fishy romance began.

  14. Gonzalo Mendez says:

    I was wondering if there is a way to get rid of the fish smell in my fertiliser?, If so I would love to know… either way a solution to reduce the odour.
    Thank you!

  15. I noticed that after being given fish fertilizer, the leaves of my avocado experienced a high level of “salt tip burn.” Avocado is very sensitive to salt. Given the expense and the other considerations in your fine article I plan to go back to pure ammonium sulfate.

    • Your problem has nothing to do with fish fertilizer. You probably just added too much. This will happen with any fertilizer. for sensitive plants, always use half of what is recommended, or even less.

    • tolga erok says:

      Although useful for many human purposes, ammonium sulfate poses some health risks to humans and animals and requires careful handling. The primary use of ammonium sulfate is in commercial pesticides and fertilizers. This substance dissolves rapidly in water, but not in alcohol and other synthetic mixtures, making it a solid addition for stabilizing fertilizers. Ammonium releases upon exposure to water and can make its way into the air in the form of ammonia gas.
      After application to damp soil, ammonium particles escape, causing an increase in the acidity level of surrounding soil. The rising acidity creates a lower pH level in the soil, increasing growth of plants and crops. The introduction of ammonium sulfate to soil also produces nitrogen, which encourages rapid growth of plants.
      Ammonium sulfate dissolves less readily than many other natural and synthetic compounds, making it an economical choice for a cheap fertilizer ingredient. This compound also serves as an herbicide by searing and ultimately killing the leaves of plants, making their removal easy. Ammonium sulfate also appears in processed breads and acts as an additive in many foods.


  16. Teh Koon Thian says:

    I had 3 ace’s of jackfruit and l’m using fish emulsion fertilizer for the past 4 have help me solved a lot of problems such as insects ,dry branches,small fruit,quality of fruit that like rusty and very hard cheap to use,1liter l can mix 200liters of water and it cost only RM 212.00 for 20 liters

    • Imagine how much cheaper real fertilizer would be?

      • Allan Teo says:

        Depends on what country. Chemical fertilizers in Asia can be FAKE and also controlled by CARTELLS and become 4x more than fish.
        Chemical Fertilizer also hardens the soil over time and lowers the PH.. The man is talking about a FARM not a garden.

        • Chemical fertilizer does not harden the soil. Nor will it lower pH unless it contains a lot of acidifying ions like sulfates.

          • Ken says:

            While it is technically correct that chemical fertilizer probably does not harden soil, chemical fertilizer does not add humus which is critical for many soils to prevent hardening. It is also true that our vegetables have between 30 and 50 percent less nutrients since we have been relying on chemical fertilizers.

          • I have always said organic fertilizer is better than synthetic – but not for the reasons most people claim. Organic matter will prevent hardening of soil by allowing nature to create soil aggregates.

            Food today may be less nutritious, but it does not contain anywhere near 40 % less nutrients. The reason for a drop in nutrition complex and variable, but it is not due to the use of synthetic fertilizers.

          • Ken says:

            It is easy enough to do a search. I got 800,000 results for “do vegetables have 40% less nutrients than they used to?” There is a lot of variance but I counted on the USDA figures. Nutrient analysis has been done since the 1920’s so they do know when it changed. The car replacing the horse and the rise of petro-chemical fertilizer are the 2 most obvious reasons.

          • Just because you get a lot of hits on google means nothing.

            Re: “The car replacing the horse and the rise of petro-chemical fertilizer are the 2 most obvious reasons.” – they are only obvious because you think they are obvious.

          • Ken says:

            Well, it has nothing to do with my opinion, I did tell you how to find out what the people who study this think. Maybe you could make a case for what is causing the loss of nutrients since you are so sure of what it is not. The very basis for organic growing is healthy soil for healthy crops. If our crops are 40% less nutritious we are starting to have a problem.

  17. Steve Finley says:

    Greetings, I enjoyed reading about your comparison of fish hydrolysate to other forms of fertilizer, the N produced and uptake by plants. A concern for me is in producing homemade FH, oil remains. You state (correctly so), oil must break down via bacterial conversion and it is a task in soil to do so. The bugs hate to expend unnecessary energy. Have you heard of a way to remove or in-process break down the oil in creating a FH, cold versus cooked?

  18. Jeffrey says:

    Living in Ontario, we always use our local CoOp to buy our organic soil supplies. Kelp(K), molasses(carbs), Alfalfa(N), corn(N), Floating fish food Atlantic Ocean sourced(N)$55 for 50lbs and of course Epsom Salts! We brew our cut grasses, nettles and comfrey during the season and finish off with fallen rotten Apple and over sweet Bannana brew for a finishing kick into high gear for the microbial life to really shine in the art of living soil! yee haw!

  19. Ray says:

    I also thought that those who argue that organic fertilizer is better might like to know that 1/2 of the nitrogen introduced by fertilizer produced by the Haber process is not assimilated by plants, and therefore ends up somewhere else in the water cycle. Often this can result in eutrophication of ponds, lakes, and even oceans which can result in fish kills and other aquatic plants dying off.

    There is also a unique problem known as “blue-baby syndrome” which results from infants consuming water containing excess nitrogen that binds to hemoglobin and restricts oxygen uptake by red blood cells.

    Here’s a link to a great TedTalk that explains the Haber process and mentions the problem of incomplete nitrogen uptake by plants.

    • The incomplete use of nitrogen is not just a problem with commercial fertilizer. The same thing happens with organic fertilizer. Any nitrogen that is not consumed by plants will also be washed through the soil into water systems.

      Some of the excess nitrogen also ends up being converted back to N2 gas.

      This is one reason to develop a good soil with enough organic matter, which in turn provides the conditions needed by microbes, which can use excess nitrogen not used by plants.

  20. tolga erok says:

    ok, here is one for you, and please dont judge the author of the post regarding this interesting concept of using ocean water as fertilizer

    • I have three problems with the reference:

      1) It is just an ad to sell stuff – so it is highly suspect.
      2) It gives no scientific references of published information to support their claim.
      3) They don’t seem to mention the fact that sodium in the sea salt is toxic to plants.

      Most soils re not deficient on the minor minerals – plants need very little of these.

      • Dan says:

        Sodium is a macro nutrient…a cation. Granted soil structure needs less of it than other cation macronutrients (Calcium, Potassium and Magnesium). Plants need it to function properly…along with all the co-factors of micronutrients and anions to make it all work.

        Your philosophies espoused here lead to additional Fungicide sales…which in turn lead to more fungicide sales. Fungicides lead to pythium, rhizoctonium, fusarium and a host of other bad guys that cause SDS, Goss’, mildew, rust, anthracnos, etc. In my decades, I’ve found there’s more to a biological system than pure chemistry and/or biology.

        Give mother nature a bit of what she wants and get the heck out of the way. Work against her and she will still win…eventually.

        • Not sure what your point is? As far as plants are concerned sodium is not a macro nutrient, in fact it can be quite toxic.

          None of my philosophies promote the use of fungacides?

      • Ken Parker says:

        Thanks you for sticking to science. No amount of sea water is going to help increase production of growth, fruits, grains and flowers.

  21. Cynthia E. Olen says:

    Mimi’s question about other nutrients that plants need besides those provided by organic material brings up a point that I need some clarification on. Native mineral based soils and their importance to plant cultivation in the home garden.
    I and my sister live in California (born and raised thank you very much), notorious for heavy clay soils with high pH. By one website’s assessment (based on web postings), we must be the coffee ground amendment capital of the US.
    I live in the Sacramento Valley, she lives in the Mt. Tehema volcanic zone, almost in the shadow of Mt. Lassen. Our soils are very different, but have the same problem in both soils being heavy clays. Hers are volcanic (dacite, andesite), mine are chiefly granitic (washed down from the Sierras mostly). They are high in trace nutrients and metals (but in different proportions), and are well weathered so these nutrients should be available, but aren’t really.
    I had a problem with iron chlorosis and some research showed that I needed to decrease the pH of my soil in order to make the iron available—the iron is there, it just isn’t being taken up by the plant roots. Hence the coffee grounds, which seemed to work actually. I also added more organic amendment since it was clear that I hadn’t added enough when I first prepared the soil for planting, and that cured the problem. The coffee grounds were a stop gap (though I still keep some around in a separate compost just in case).
    My sister seems to have a different problem—low potassium. Her vegetables and other plants fail to flower or only put on a few weak flowers. She uses compost she made herself blended with the native soil. Her soils contain potassium (moderate levels), but the plants aren’t taking it up. It might be that her soils aren’t sufficiently weathered to make the K available, but I’m wondering if she needs to do something else to help with K uptake. Might her soils also be too alkaline, as in my problem with iron uptake?

    Myth? I have had people tell me that the native soil is unnecessary and if it is a problem soil, like here, then I should dispense with it altogether and use nothing but potting soil and compost in raised beds. I don’t buy that. Nature seems to do okay with mineral-based soils as long as there is some organic matter in the mix. I feel it is important to use the native mineral soil. Yes? No?

    • First of all, although coffee grounds are a good organic addition to soil, they don’t lower the pH – that is a myth.

      In everything you say, I did not hear you say you had your soil tested? If you did not test your soil, your conclusions about what is low or high may be wrong. Start with a soil test.

      Chlorosis is actually NOT a sign of iron deficiency. When the plant can’t get enough iron it will show something called interveinal chlorosis – they are not the same thing. Even if you had interveinal chlorosis, it does not mean you had an iron deficiency. High levels of other nutrients can tie up the iron and keep it from plants.

      Looking at leaves is a popular way to identify a nutrient deficiency – but this does not work. There is almost no nutrient deficiency you can identify this way.

      A pH under about 7.8 will grow most plants just fine. The exception are some acid loving plants. I grow almost everything in 7.4 clay.

      Even if you made raised beds, the recommended addition to those beds would be native soil. You might add extra organics, but it should still be soil based, especially in your climate. Potting soil drys much faster than clay soils.

      Adding organics will buffer things in soil. It buffers pH and it buffers the availability of nutrients. Keep adding organics. If a soil test shows a deficiency – correct it with fertilizer.

  22. Keerthy says:

    I am a supplier of liquid fish fertiliser in Darwin Australia to all the big scale farmers. Do u reckon $2 per litre for a perfect quality fertiliser is good?! Just need to know whether my costing is good.

  23. JTrev says:

    In regards to the sustainability and sourcing of fish fertilizer products, I like the model that Carpe Carpum out of Idaho uses, i.e., capturing invasive European carp that have infiltrated the local eco system and turning it into fertilizer. The method they use is cold-hydrolysis, which seems to me a better option then emulsion methods.

    Here is an article from Sunset magazine. As an interesting sidenote, the company harvests fish from Malheur Lake (recently in the news) as one of the approaches to cleaning it up.

    • The idea is a good one. Removing an invasive species and using it productively is excellent.

      I do have a problem with the company. They provide no information on their web site about what is in the product so you can’t evaluate the product and the cost. Secondly, the little they do say on their web site shows they don’t know much about fertilizer and plants. Hopefully this will improve as the company matures.

  24. Patty says:

    I discovered a free fertilizer which is readily available and high in nitrogen. I can get it on a daily basis. Don’t even have to leave the house, in fact. It’s urine!!! Diluted one part urine to about ten parts water. Please try it before you slam the thought! I use it on veggies and all. Every.single.plant loves it!!! Makes my veggies taste so delicous. Of course I thought it was weird too when I first heard of it. But if you try you will not be disappointed!!

  25. Cynthia E. Olen says:

    I get your argument here—a very focused, purely empirical, purely economic statement about the basic chemical value of plant nutrient sources vs cost. An ion is an ion is an ion—no matter its source, its all buffet to a plant. I also get your argument about false claims used by manufacturers to boost the desirability of their product, and kudos to you for busting their chops about it, especially at 25 bucks a gallon. However, the chemical industry makes all kinds of false claims, too, especially about the safety of their products in these safety-conscious times. Just sayin’.
    Most of the respondents here seem to think that you are attacking fish as a source of fertilizer. You aren’t—I can see that. Unfortunately, in your efforts to reiterate your basic statement that plants can’t tell the difference between nutrient sources, some of your responses make you sound like a chemical industry shill, which naturally turns up the volume on opposing shouts. Interesting debate ensues.
    Here is my problem with commercially available fish emulsions and fish meals: They do not come exclusively from scraps left over from processing human food—which makes it sound like fish emulsion is this eco-friendly waste-not process that we should embrace as a small-footprint Good Thing. Instead, the vast majority of fish fertilizer comes from targeted fishing of species which are deemed undesirable as human food—so-called “industrial” species. However, these fish are valuable food sources for other organisms. In some places, food-fish stocks—such as anchovy and sardine, as well as krill—have been devastated by over-harvesting for the fertilizer and animal feed industries. The result, of course, are equally devastated losses of large fish, sea birds, pinnipeds, and cetaceans in the over-fished areas, as well as the overall ecological imbalance that always accompanies the wholesale loss of a key link in the chain.
    So, while using fish fertilizers allows the organic gardeners and farmers to give a nice, satisfying, righteous middle-finger “screw you!” to BigChem, the use of these products carries its own heavy weight in terms of negative ecological burdens—something that the manufacturers don’t tell you in their promotional ads.
    The best thing? Use the fish, yes, but don’t buy commercial versions which come from the industrial fisheries. If you are an angler, or just someone who eats fish regularly, use your own scraps and trash fish by-catch to make your own emulsion. You can also get fish waste from restaurants, grocery stores, butcheries, and if you live near a fishing town, straight off the docks there. All it really requires is a lidded container, fish parts, a carbon source, occasional stirring and patience. There are plenty of instructions and tips online on how to make your own emulsion.

    • You understood the post and the comments very well. Many of the comments are from people who did not read the post.

      You said “Here is my problem with commercially available fish emulsions and fish meals: They do not come exclusively from scraps left over from processing human food—which makes it sound like fish emulsion is this eco-friendly waste-not process that we should embrace as a small-footprint Good Thing. Instead, the vast majority of fish fertilizer comes from targeted fishing of species which are deemed undesirable as human food—so-called “industrial” species. ”

      I was not aware of this and have done some digging, and you are right. It is clear that many of the products on the market are NOT made from fish waste products. I find that very upsetting and will do a future post about this.

      • Cynthia E. Olen says:

        Please do! Gardeners of every stripe need to know the real costs of what they are using.

      • Kate says:

        Hamakua Gold out of Hawaii uses waste of the fishing industry and ferments its product. It is like a probiotic for your plants and soil and a sustainable product!

        • If they use fish waste – that is a good thing, but it is not “a probiotic for your plants” – it is just nutrients like every other fertilizer.

    • Yes, this is exactly why I am reading all the comments in this forum. I live in Maryland and just recently the Atlantic States Marine Fisheries Commission did a disservice to the very important forage fish species “menhaden” and will not be managing them in an ecologically sound way or with a scientifically based method, all because of the powerful lobbyists that represent the Menhaden Fisheries Coalition (sounds like a group to protect the menhaden, but it’s just a group of companies that exploit this tiny yet very important fish). There is one BIG company headquartered in Virginia called Omega Protein that uses plane spotters to find the big schools and then nets them to make fish oil vitamins and pet food and fertilizer and is responsible for removing about 80% of the allowable catch annually. As the previous commenter said, it’s not actually “byproducts” from fish used for human consumption, which if that’s what people think, then using fish fertilizer sounds like a good thing that doesn’t let anything go to waste, but that’s far from the truth. This fish is in danger and because of corporate greed, striped bass and many other fish that depend on this species as an actual food source are at risk. If there’s no reason to use fish fertilizer over another kind of fertilizer, people should get informed and stop buying it.

      Have you written a follow up post about this yet? Thank you!

  26. Josh says:

    I have used fish emulsion and miracle-gro and have had positive results with both. From what i have gathered, people have either skimmed over the article or just looked at the headline and jumped to the comments section. This seems to be common and also enjoyable. People tend to cling to what they believe in, even with counter evidence. I have a small garden, so it would be no problem to go fishing on the weekend to supply it with some fresh fish if thats what i wanted, but a farm or larger garden would take some serious fishing. I am no expert, but my plants look healthy and grow well either way.

  27. Sam Fleming says:

    There is an indoor tilapia Aquaculture facility in my city that donates culls to our organization. We could get several hundred pounds a month what are your thoughts on turning farmed tilapia into fish hydrolysate?

  28. Caleb bartee says:

    So I’m gonna put in my two cents. I don’t know enough to be like “oo this is the best or this is the best” but when I was trying to find something for my roses that was pesticide free and wouldn’t burn the roots fish fertilizer was the cheapest option, and I must say my roses are thriving!

    • I’d like to see your data. How much did you pay, how much volume did you get, and what was the NPK analysis of the product you bought. Product name would also be useful to have. I will be very surprised if it was a cheap source of nitrogen, but the data will show us.

  29. Wayne Hartman says:

    I finally found a point I can totaly disagree on. Synthetic ferts are petro ( natural gas ) based. We frack the ground to release natural gas to burn and make fertilizer. Fracking and its waste water pollut ground water. Oklahoma is frack capital of the world and since we started fracking we are earth quake capital of the world.

    • Synthetic fertilizers are not petro based – that is another myth. It is true that making nitrates does require an energy input and natural gas may be used. But it also takes energy to make fish fertilizer.

      You might be right that synthetic fertilizer is not the most environmentally friendly options.

      • Old Woman says:

        Sorry, Robert. You’re wrong. The nitrogen in synthetic plant fertilizers are made with petroleum products–specifically natural gas. Look up the Haber process.

        • I am quite familiar with the Haber process. Petroleum products are defined as “materials derived from crude oil (petroleum) as it is processed in oil refineries”, Wiki.

          The Haber process: “The process converts atmospheric nitrogen (N2) to ammonia (NH3) by a reaction with hydrogen (H2) using a metal catalyst under high temperatures and pressures:

          N2 + 3 H2 → 2 NH3 (ΔH = −92.4 kJ·mol−1) ”

          No oil is used in the reaction, so the production of nitrogen is NOT a petroleum product.

          If every product made, that used some type of energy, eg natural gas, was classed as a petroleum product, then every product in the work would be a petroleum product, including fruits and vegetables which require energy inputs.

          • Nick Follett says:

            Hi Robert,

            For somebody concerned about long-term sustainability of non-renewable fertiliser sources (e.g. mined phosphate), what would you recommend for an initial indoor growing phase (under lights) on a largely inert substrate (think 1:1:1 perlite/vermiculite/coir)? From seed to seedling, and then establishing the young plants.

            Some of the plants will be transplanted to a vegetable garden with quality soil, where we have access to local, free resources (some manure, lots of coffee grounds, comfrey tea etc.)

            But for the container grown plants – likely to be mostly salad greens, basil, general leafy vegetables – which will remain indoors, what’s the best approach? I have no special attachment to the ‘organic’ label, I’m just sensitive to renewable and non-renewable resources.

            My initial idea was to use prilled urea as a nitrogen source, although I’m concerned about acidifying the soil.

            I’d really appreciate your input; my reading has brought me here and you seem like you actually know what you are talking about.

            Thanks in advance,


          • When I grow seedlings for the garden under lights, I don’t normally fertilize them very much. I do grow them in a peat based mix, like Pro-mix. Near the end of the growth cycle I do apply some water soluble fertilizer, but I don’t use very much. A small pail lasts me 15 years.

            The key to understand is that all nutrients are the same – no matter their source. If you want to be more sustainable, use any fertilizer made from waste material, compost or fish fertilizer that is really made from fish waste and not live fish –

            The problem with being sustainable is trying to figure out which product actually harms the environment the most. For example, composting produces CO2. Is that worse than mining phosphate? Probably, but maybe not – we just don’t have the data.

  30. All we ever do around these parts is each fall we bury fish and then put kelp on top a bit of dirt to hold it all down.
    all summer long we just water no need to buy anything.

  31. brad mayeux says:

    chemical fertilizers are solubilized with water.

    at this point, the plant has NO CHOICE but to take it up…
    this is why it is possible to over-fertilize plants and burn roots.

    These chemicals kill the microbes in the soil, and these microbes are the basis for plant health.
    Chemical fertilizers change the epidermal cells and guard cells, and keep the stomata open, which can make the plant more prone to disease.

    When the plant takes up chemical salts, it needs more water,
    so… it takes up more water than it needs to.
    This makes it “bloat” and appear larger.

    The cell walls are actually thinner and are more susceptible to disease and pests.
    Pests can notice this , and will attack this plant, and leave other nearby plants alone.

    The gardener will then blame something else, and go and buy pesticides which will further kill the microbes in the soil.

    This is wonderful for chemical companies, but, not so much for the rest of us.

    • Your comments are not factually correct.
      1) the ions absorbed by plants are the same no matter if they are snythetic or organic.
      2) There is no evidence that fertilizers, when used correctly, kill microbes – another organic gardening myth.
      3) Once absorbed, fertilizer nutrients or fish nutrients will have the same effect on stomata
      4) You are confusing the term ‘salt’ with fertilizer. all nutrients taken up by plants are ions of salt – again fertilizer ones are identical to organic ones.
      5) the whole story about taking up too much water, bloating, and thin walls is not true – if you beleive it is provide some scientific evidence to support your statement.

      • Hilary McKenzie says:

        Since fertilisers have a salt rating which shows their effect on salt concentration in the soil (because of the risk of seed and root burn) it is not unreasonable to assume that at higher rates they will also be causing harm or change in the soil ecosystem. There are choices when a particular nutrient is needed. Some of these choices are organic. So in my opinion, all nutrient is not the same.

        • I don’t follow your comment at all?

          What is a ‘salt rating’? Salt concentration is easily calculated – you don’t need a salt rating? Fertilizers only burn roots if too much fertilizer is added. Yes higher rates will cause damage, but nobody is recommending to use higher rates.

          Whether you get your nutrients from commercial fertilizer, or from fish or from plant compost – they are all salts! A nitrate molecule from any of these sources is identical. See What is Organic Fertilizer for more details.

          • Hilary McKenzie says:


            I was responding to the comment by Brad Mayex. I agree that ions are the same whether they come from fish of from synthetic fertilisers but fertilisers are not applied in the ionic form, they are applied as salts, and all fertiliser salts are not equal in their risk of change to osmotic pressure across plant membranes, and therefore risk of root or seedling burn. It is also my belief that the same risk extends to harm to soil microbes

          • Correct, fertilizer is usually applied as a salt. For it to enter the soil, it must dissolve in water and when it does this it becomes ions.

            Ions do change osmotic pressure – all ions do this, both synthetic and organic.

  32. portkelly says:

    i just came to this site in my search for why the cucumber i put in my stew kind of ruined it.

    i bought it from an organic grocer and did not store it in my fridge which doesn’t have any fishy anything in it. but my stew smelled strongly fishy…my roommate thought i had put fish or cod liver oil into it. no.

    i recalled an in-law telling how strawberries gave her a bad reaction that she had only gotten from sea food. she said she had a sensitivity to iodine. she told me that they use fish fertilizer on strawberries.

    so i knew i wasn’t crazy when i tasted something fishy with the cucumber.

    i have now just learned that both kelp meal and fish emulsion are used on some produce–especially organic.

    so now i’ve decided to give up on some of the organic produce.

    and for the above reason, i hope that Robert Pavlis is successful in discouraging the use of those fertilizers.

    • Fish smell and fish flavors will NOT be transmitted into plants. The complex organic molecules must be broken down in to simple nutrients before plants can absorb them. By that point they are no longer identifiable as fish molecules.

    • Zacchary carter says:

      Why would you even put a cucumber in a stew it is a salad vegetable
      And water the roots and ground and not spray direct onto the produce your going to eat
      I don’t believe your argument just your bad cooking

    • Hilary McKenzie says:

      …but it could come from surface residue on leaves or in this case fruit if they are not washed well before use, as any produce should be, whether organic or not.

  33. The_Bugman says:

    To the Author: Do you suppose there would be a benefit / difference between store-bought and homemade fish-hydrolysate?

    The cost pretty much goes out the window, ($0.80 ea. for a few cans of sardines and $4 for a reusable bucket), unless you like adding expensive additives such as kelp meal, etc.

    It’s my understanding that this method allows you to introduce not only the macro-nutrients to feed the microbes, but the microbes and bacteria itself, to the soil, since you’re not treating it to remove the bacteria before packaging it (done with all store-bought versions, so the bottles don’t explode from the pressure of continued fermentation).

    • You can’t compare an 80 cent can of fish with a $4 bucket of fish emulsion without looking at the numbers. How much nitrogen does each product supply? Then compare the cost on a Kg basis.

      A can of sardines is just a can of sardines. It is a few ounces/grams of organic matter. No matter what you do to it, it is still only a few ounces/grams of organic matter. compared to the size of a garden bed – that is nothing.

      Your soil already has all the microbes it needs. You don’t have to add more. Your goal as a gardener is to feed the microbes you already have so they grow and prosper.

      I have seen NO scientific evidence that adding microbes to garden soil makes any difference in plant growth. If you have a source i would love to see it.

      I also think it is poor practice to take good food and dump it on the garden, when people are starving.

    • Cynthia E. Olen says:

      Bugman, do not even consider using tinned fish as a fertilizer source! They are usually packed in oil which simply turns into a waxy substance. The fish is cooked and sterilized, so lacks living bacteria that help with fermentation. Cooked flesh decomposes slowly. And tinned fish is loaded with added NaCl salt. It is also a deplorable waste of edible food.

      If you want to make your own fish emulsion, use raw fish. Like I stated in my post before, you can get raw fish scraps from several sources. Just a note: When you do go fish scrap foraging, make sure you get the guts, too, if you can—this is where most of the decomp bacteria come from.

      Foraging for scraps is a little challenging, true. You have to cultivate contacts with people who can provide them to you, and you have to be conscientious in your commitment both to your DIY emulsion project and to your contacts. Note: If all you want is a small amount for a one-time emulsion project, let them know so that they will not be saving waste for you unnecessarily. Commercial sources generate the waste everyday, so they would not need to save it. You could probably collect a fair amount just by walking in early in the morning and asking for it on an as needed basis. Smaller producers, like a friend who fishes on weekends, would probably have to save the waste for you—help them out by giving them a plastic bucket with a good lid that they can take with them on their fishing trips and make arrangements to pick it up asap upon their return.

      Asking for fish scraps from a stranger can be a little daunting, yes. The potential supplier stares at you, tilts their head like a puzzled cat, and says, “You want fish offal for what?” So, it may take a little patient explaining.

      Almost everyone knows someone who fishes—ask that person to save the scraps and trash by-catch for you. If you live in a seaport town with a commercial fishing fleet and local cannery, talk to the boat captains and the cannery manager. Talk to the restaurant managers and head chefs of your local restaurants (including big chains, though you may find them less cooperative than small indies). Talk to the meat managers and butchers of your local grocery stores who process raw fish themselves. If you buy and eat fish, save the uncooked waste portions (heads, fins, skin, raw bones—whatever you’ve trimmed out before cooking) and add them to your emulsion bucket. Heck, you could even approach pet and aquarium stores for their culls and dead fish. If you are fortunate enough, like Sam Fleming in an earlier post, to live near an aquaculture facility, you could approach the manager about getting their culls and dead fish. Hatcheries may be a another source.

      The beauty of this approach is that, except for the gas you use to get to the sources, it is pretty much free to you. Way cheaper, anyway, than buying emulsion.

  34. Starletta says:

    ….Meant to say that the plants require less insecticide/fungicide input grown w/fish& kelp vs synthetic NPK in last paragraph. But sheeeeewt. Since it’s been established that the amino acids in the hydrolysate (fish, whey, soy, poultry litter/feather meal, whatever the source) act as chelators in the soil for the sequestered & otherwise unavailable nutrients, the plants DO require less actual fertilizer input from the farmer when grown with fish hydrolysate vs ammonium or calcium nitrate.


    • It is true organic mater added to soil, helps hold nutrients in soil. And higher organic levels means that you need to fertilize less over time.

      But plants still use the same amount of nutrients no matter the source.

  35. Starletta says:

    As someone who has done multiple side by side comparisons of very high value consumable crops, I will say that fertilizing with hydrolyzed fish & kelp meal improve product appearance, aroma, flavor, fruit/flower size, fruit/flower shelf life, & provides a MEASURABLE increase in the plant resins & aromatic oils. My flowers test 10-15% higher for essential aromatic compounds when grown with fish hydrolysate & mechanically dried kelp meal VS when grown in sterile medium with with synthetic fertilizers. If my crop nets me an additional $1-2000 versus using scotts or miracle gro (or even an expensive ‘hydroponic’ bottle of mineral salts – one with multiple chelates), AND I can reuse my medium because it is not all locked up with mineral salt imbalances, it seems to be a smart $50 investment for the fish & kelp.

    Feed the soil, not the plant. Plants fed fish and kelp also require less fertilizer input. Higher brix levels in the plants ensure that the plants will be more able to fight off any possible pests by themselves without me spraying them with pesticides/fungicides.

    • Please provide to support your findings.

      Re”Plants fed fish and kelp also require less fertilizer input” – that is clearly not true. The amount of nutrients a plant takes out of soil is exactly the same no matter where the nutrients come from.

      Do higher brix ward off pests?? I’d like to see the data on that. In fact, if anything, I would expect a higher brix to invite more pests like aphids due to the higher sugar levels. You might be growing your plants well which can lead to higher brix, and less pests. But that does not mean that there is a causation relationship between high brix and number of pests. The plant that is able to produce higher brix is usually healthier and therefore also able to produce more natural pesticides.

      • Bobbo says:

        All I have to say is that you should read teaming with microbes and teaming with nutrients. It will educate you on how you feed the soil and not the plant.
        Synthetic nutrients destroy the natural life of the soil, especially nitrogen.

        • Teaming with Microbes has some good points in it, but also has several incorrect statements in it.

          You can’t feed the soil – soil is not living! Soil is the mineral part of what is in the ground plus organic matter. None of this is living. Soil does have a lot of things living in it.

          The statement “synthetic nutrients destroy the natural life of the soil, especially nitrogen” does not make sense for two reasons:

          1) Synthetic fertilizers when used appropriately do not destroy the natural life forms in soil – that is a commonly held myth.
          2) Nitrogen is not a natural life form!

          There is absolutely no difference between nitrogen from synthetic fertilizer and nitrogen from an organic source. to better understand this have a look at

  36. Mike says:

    So in summary, fish fertilizer is a myth because you find it too expensive? Even though people have been using it before your time?

    • If you took the time to read the post you would know that what I said was “Before I go any further let me say that there is nothing wrong with using fish fertilizer. It will help make your plants grow. I have two problems with fish fertilizer; it is extremely expensive compared to other sources of fertilizer and many of the claims for it have no basis.”

      People before my time used real fish that they collected – not the over priced, over hyped products being sold today.

  37. Hilary McKenzie says:

    There is good evidence (fully replicated scientific trials) which show that fish (and some other widely used organic preparations), have a significant affect on biological activity in soil. Since microbes are extremely important in nutrient cycling, plant access to nutrient, biological control of pests and diseases (to mention a very small number of their functions) I find it extraordinary that people continue to look at this only from the point of view of nutrient supply. I also find it extraordinary that a microbiologist or an entomologist or even a soil scientist, will have a completely different viewpoint than what is promoted by mainstream fertiliser companies who only promote one aspect of soil health (that of soil chemistry).Growth of healthy plants is a result of a complex interaction between soil physical characteristics, soil biology and soil chemistry.(all modified by climate, altitude and multiple other environmental factors). ie limitation comes from any factor which is limiting. There is no magic solution. If there is a shortage of nutrient to a plant, then either the nutrient needs to be supplied or the farmer needs to improve the ability of that plant to find the nutrient that the plant needs. There is more than one way to skin a cat! Since farmers have different values and goals, their choices on how to achieve this will be different. What is needed is an open minded approach from both ends of the debate, so that farmers are able to get the information that they need, in order to be able to make sensible, sustainable decisions, without the vested interest of those who supply products (both organic and mainstream) getting in the way……end of rant 🙂

    • No one doubts that fish fertilizer will have an effect on soil. Any fertilizer, organic or synthetic will have such an effect.

      But does a fish extract perform better than another source of nutrients? That is a different question, and I don’t think there is good evidence that this is true, for the ‘fish extract’ products on the market. If it is, I would like to see a reference. You say that “fish (and some other widely used organic preparations), have a significant affect on biological activity in soil” – Ok so what. I don’t doubt this. I can throw almost any organic material on soil and get increased biological activity.

      To be of value to gardeners, these studies need to show that when fish extracts are applied to a garden, they produce better plant growth than other sources of nutrients. People are trying to equate biological activity to better plant growth, and that is incorrect. That does not mean that some types of biological activity does improve plant growth – it does in some cases. But the one does not necessarily follow the other. In fact increased biological activity can harm a plant if the microbes being stimulated are pests.

      I also think there is a big difference between adding real organic matter like raw fish, and adding extracts. Extracts are much closer to synthetic chemicals as far as their value to soil goes.

      Your statement “There is no magic solution. If there is a shortage of nutrient to a plant, then either the nutrient needs to be supplied or the farmer needs to improve the ability of that plant to find the nutrient that the plant needs. There is more than one way to skin a cat! ” is absolutely true.

  38. Thomas Lansing says:

    Hello Robert Pavlis,
    Thanks for writing a nice blog. The section “Is Fish Fertilizer Organic?” could use some clarification.

    1) Most commercially available hydrolysates and emulsions do not use odor inhibitors and which are very benign. Examples of odor inhibitors are: Tea tree oil, Lavender, Mint extract. These odor covering solutions are organic. Some are even organic certified in their own right. I don’t add them to my own hydrolysate because they are expensive.

    2) The blog is correct, phosphoric acid or H3O4P is an inorganic acid. It is important to know what that means. H3O4P comes from minerals (salts) and it is not going to hurt you, or your plants, or the microbes near your plants. The potential harm from this acidic salt is that it is corrosive. How corrosive? Very corrosive at 85% (typical liquid state for H3O4P) and hardly corrosive at all at 1% (the amount in fertilizers). The pH for fish protein hydrolyses and most emulsions is about 4. For perspective, this is less acidic than tomato or orange juice.

    3) We should add this information for your more interested readers. Some emulsions use mold inhibitors, like sodium propionate. These are mold inhibitors that are used in things like bread and grain storage. That white powder on a bun from a fast food burger or a pack of twelve white bread hot dog buns. That is sodium propionate, and some of it gets on your plants. In the fertilizer, it can make up about half a tenth of a percent volume (.05%).

    For your really interested readers have provided some additional information.

    General info about organic acids –

    Nitty gritty on the three main types of Phosphoric acid –

    Trailing wheels version –

    For our graduate student research readers –

    4) Also… I agree there is a lot of hype by fertilizer companies about the differences between hydrolyses and emulsions. The significant difference is that emulsions are heated. The heat kills many important microorganisms. Your microorganisms are hugely important! Do not roast your protozoans, do not fry your endomycorrhizal fungi, do not endanger your endogenous bacteria. If, as you claim, you have been having trouble finding articles on the topic from unbiased sources try some of these:

    5) Also some clarification about the fish oil… The argument for fish fertilizers is that the oils present in fish protein based fertilizers act as a spreader sticker, or an agent to help adhere the nutrients to the plants. This is a benefit to the plants as it increases the uptake of available Nitrogen. Plus we could re-work your math all day with other fish based fertilizers that have higher percentages of available Nitrogen. Many are closer to 5%. For me a 3.8% N fertilizer with higher uptake (thanks fish oil) and longer amino chains on the proteins (thanks cold-process hydrolysate) to feed my endomycorrhizae is far superior to the chemical alternative.

    Last thing. Be careful making your own fish fertilizers at home with salt water fish. They can be salty. I also do not recommend using waste from commercial aquaculture unless you are sure they do not use antibiotics. The same goes with cow manure. My absolute preferred fertilizer over time is fish protein hydrolysate with some cow or chicken poo every now and again to balance your P and K. A mixture like this is wonderful for developing organic matter %.

    Okay, I got carried away. Cheers.


    • Thanks for all the great info.

      Re: your #4. You say “The heat kills many important microorganisms” – that is true. However I don’t think this is a bad thing. The microbes in and on fish are going to be quite different from the ones in the soil – completely different environments. There is no value in adding microbes on fish to your soil.

      After heat treatment, the resulting material is food for soil microbes – this is true if heated or not.

      The links are about hydrolyzing protein. None of them look at the effects of different processes on plants. I was looking for a study that compared different processes on actual plants grown in the field.

      Re: 5. “oils present in fish protein based fertilizers act as a spreader sticker, or an agent to help adhere the nutrients to the plants”. Do you have proof of this? Sure oils would stick to plants, but that does mean it is good for plants. Nutrients need to go into soil and be absorbed by plants. Having nutrients ‘stuck’ to oil in the soil is no benefit to plant roots.

      Re: “increases the uptake of available Nitrogen” – I find that hard to believe. Nitrogen is absorbed as nitrate and ammonia in water around the roots. Oil would not help. But if you have a reference to support this I’d be interested in seeing it.

      Re:”longer amino chains on the proteins (thanks cold-process hydrolysate) to feed my endomycorrhizae is far superior to the chemical alternative” – do you have proof? all of these proteins need to be degraded to simple nutrients like nitrate before plants can use them. Having longer chains of amino acids is not going to be of any benefit. Ans organic nutrients are not far superior to chemical alternatives. Once they are converted to nitrate molecules – plants can’t tell them apart. See

    • Cynthia E. Olen says:

      To Thomas Lansing: “Be careful making your own fish fertilizers at home with salt water fish. They can be salty. I also do not recommend using waste from commercial aquaculture unless you are sure they do not use antibiotics.”

      I agree with you on the antibiotics—they can attack the very bacteria in the fish and soil that you need. However, the ocean fish comment is probably inaccurate.

      First of all, nearly all commercial fertilizer derived from fish, whatever its form, comes from ocean fishes. In my earlier post, I discussed the sources of fish-based fertilizer. It is not a sustainable source and should be avoided if possible.

      Second, the “saltiness” of fish tissues (or any animal tissue) is about the same across fresh and salt water. Fish kidneys are very efficient at removing excess salt from the body, so there is little or no difference between fresh water and ocean fish when it comes to the salt content of their tissues. You may, however, want to wash off the sea water still clinging to the fish’s skin and mouth.

      • Antibiotics will decompose just like any other organic chemical. I do agree we want less in the environment, but I don’t see it as a concern in fertilizer.

  39. Hilary McKenzie says:

    You are still talking about amounts of nutrient and its direct effect on the plants that grow within that system. The most productive ecosystems on earth grow with no applied fertiliser. I agree with you, when you say that any input must produce an economic benefit for farmers (or gardeners). I also believe that the soil ecosystem of our farms and gardens is hugely disrupted compared to those natural ecosystems. I believe that the way of the future is efficient use of fertilisers which have minimum impact on soil biological systems and use of products which help to activate or enhance natural systems in the soil. There is scientific evidence that use of a number of products including fish hydrolsate and fish emulsion produce a measurable increase in both numbers, and activity of soil micro organism, and that use of high rates of high analysis fertilisers, particularly nitrogen fertilisers, produce the opposite, over time. So the question remains, is this of economic benefit?

    • The statement “most productive ecosystems on earth grow with no applied fertiliser” is not true. It is true for commercial fertilizers, but fertilizer is still applied, and plants can’t distinguish between the two.

      The statement “There is scientific evidence that use of a number of products including fish hydrolsate and fish emulsion produce a measurable increase in both numbers, and activity of soil micro organism:, is certainly true. Adding nutrients of any type to soil will have this effect.

      The statement “use of high rates of high analysis fertilisers, particularly nitrogen fertilisers, produce the opposite, over time” us also true, if by “high” you mean amounts in excess of recommended amounts. However, when commercial fertilizers are applied in amounts that make sense to replace deficiencies, the evidence is clear, that they do NOT destroy soil structure or affect soil life in a detrimental way.

      I do agree with one point you make. We should not apply nutrients, as commercial or organic products unless we know there is a need.

      • Hilary McKenzie says:

        I am really enjoying the debate, so I hope you don’t mind more questions. Are you saying that the only stimulation of microbial activity is from nutrient supplied? That there is no such thing as an activator? Are you also saying that no harm is done to any soil microbes by commercial fertilisers if they are applied at the required rate? There is then a whole argument about required rates vs recommended rates, when these are driven by commercial interests. It is a minefield out there!

        • Microbes are just like other living things. Food stimulates their growth. they need nutrients to grow, but they also need the right temperature, and the right amount of oxygen.

          Activators are usually a mixture of bacteria and nutrients. For more info on this see

          “Are you also saying that no harm is done to any soil microbes by commercial fertilisers if they are applied at the required rate? ” – correct. a bacteria or plant can’t tell if the nutrient molecule is from a commercial fertilizer or an organic source, because they are identical.

          “There is then a whole argument about required rates vs recommended rates, when these are driven by commercial interests. It is a minefield out there!” a farmer bases their nutrient application on soil tests, so this is not a problem – they don’t follow package instructions. Howe owners don’t get soil test done and just guess – many times based on folklore or something stupid they were told on social media. If you don’t know what nutrient is missing from your soil – how can you expect to add the right nutrient, in the right amount???

  40. carlos velarde says:


    well,I a afraid I dont understand your mathematical or financial explanation of the fish emulsion. You claim it is very expensive and poor in nitrogen. I have a 3 x 1 square meters of cranberry plot and I make my own fish fertilizer. I buy 500 grams of fresh fish for 1 dollar and a half plus other ingredients and that is enough for the whole year.Even other plants benefit from this fertilizer.

    • That is cheap fish – $3 per Kg. How much does your nitrogen cost? Fish meat is 15-20% protein. Assuming you are buying whole fish, it would be at the low end of this range. 1Kg of fish is 150g of protein. But only part of the protein is nitrogen – 16%. So the 1 Kg of fish contains 24 g of nitrogen. So you are buying 24 g nitrogen for $3. So you are paying $12 for 100 g of nitrogen, compared to commercial fertilizer at $0.91 for 100 g.

      You are adding 500 g of fish to your garden plot for $1.50 – that is 12g of nitrogen (500 x .15 x .16). As commercial fertilizer this would cost you just $0.11.

  41. carol says:

    trying to read the articles (below this box on and they keep moving before I can finish reading them. Is there a fee to be able to actually read the article?

    • You must be talking about the promotions at the bottom of the post. Just click on the one you want to read and it twill take you to the page. Everything on this web site is free.

  42. I have been terribly neglectful with my blog and just ran across your article using my picture. I am so flattered. Thank you!

  43. Hilary says:

    Perhaps the benefit is in the fact that it is processed by a microbe. ie it is a food source. These are the same microbes which are cycling nutrient, and converting it to plant available forms. Without microbes, ever increasing amounts of the nutrient our plants need will have to come out of a bag. I agree with you if all we are looking at is NPK etc, but we all know that it is a lot more complex than that.

    • Robert Pavlis says:

      I am sorry–I don’t understand your comment. I did not say fish fertilizer has no benefits. I agree that microbes will use the nutrients and yes they are very important to healthy soil. The point of the post is that fish fertilizer is a very poor and expensive choice. Most other options are less expensive and also feed the microbes.

      • jeremiah says:

        Well here in the tropics it is a sustainable soil amendment.Heavy rain fall, That oil helps leaching,Cold process has living enzymes doesn’t matter NPK your chemical only feeds your plants and runs off to destroy more ground water. When making fish 50gal of shredded fish makes 1000-1 dilution rate which = teaspoon a gal .. Protein in your soil is food, They have been using it way before us and way after.. Fish is the most amazing soil amendment i have ever used and consider your blog a insult to Fish fertilizer and people making the world a better place without chemicals.

        • I think you missed the point of the post. I never said fish were not sustainable, nor that it was not a good fertilizer. I also did not discuss the situation where you live near available fish and can make a 50 gal batch for yourself at low cost.

          Most gardeners need to buy the material in small containers – and then it is a very expensive choice.

          Living enzymes are just proteins, and there is no evidence that they are beneficial to plants except for the addition of the nutrients. Protein in your soil is NOT food for plants. It first needs to be broken down into basic nutrients and then it becomes food for plants. Once that happens there is no difference between protein and commercial fertilizer. to understand this you might want to read Organic Fertilizer – What is its Real Value.

          Fish are chemicals! Plants can’t grow without chemicals.

          • Tim says:

            To solve this for everyone.

            Mr.Robert says fish based nutrients are the same as synthetic salts as far as your plants are concerned. They are also cheaper.

            Everyone else says, so what?
            We will pay more for (or make our own) fish based fertilizer (or any other organic amendment) because it is more friendly to the ecosystem and doesn’t support the petro-chemical industry.

            Which is worth every penny spent. (or unspent!)

            The End.

          • That is a valid point. Supporting an organic industry is a good reason to buy fish fertilizer. Lots of people decide to pay higher prices to buy organic. And if the fish fertilizer industry or its proponents were using this as the reason to buy I would have no problem with it. Unfortunately they chose to make up false claims about their product instead.

            As far as not supporting the ‘petro-chemical industry’, your point is incorrect. Fertilizer production is not petro-chemical based – something that is on my list of things to write about.

          • Mimi says:

            Thank you the information, it gas opened up a good and important conversation… I would like to what do you think about adding sugar to the soil since sugar will feed the microorganisms? I hope this is not a stupid question.

          • No question is stupid and lots of web sources promote the addition of sugar to soil. Microbes like sugar and can use it as a food source. It will increase the population but only until the sugar is used up. Then the population crashes.

            Although sugar is organic it does not provide many of the benefits of adding more complex organic molecules that you get from plant material, manure or compost.

          • Mimi says:

            Thank you for answering my 1st question. Hopefully this second question will be my last, but I want to know if compost, manure and plant material is all plants need to get all their nutrients? Of course beside water, sun etc…

            Or better yet, how do YOU grow your plants successfully w/o the use of expensive fertilizers?

          • Plants need basic nutrients. It does not matter where they get them from. Many are naturally in soil. Others come from decomposing organic matter.

            Think of nature. Who fertilizes the plants in the woods? No one. So clearly plants don’t need to be fertilized provided that the organic matter they produce stays whee they grow.

            I mulch with wood chips which provides some nutrients, and I leave organic matter in the garden. I don’t fertilize.

            In a veg garden you remove produce, and therefore you need to add some nutrients back. I like to use straw for nutrients and weed suppression.

          • Mimi says:

            Thank you.

          • Return your pee and poop to the soil …

          • Nick Follett says:

            Does a bear “fertilise” in the woods?

          • Not really. Bear droppings will decompose and add nutrients to the soil, but consider this. If the bear was not there, the food it eats would fall to the ground and decompose providing the same nutrients. So the bear is not needed to add nutrients to the soil.

          • waheed says:

            what about fish blood,,,that left while cutting n cooking,,,have found benifit in my roof garden,,,what r the cons…

          • Anything organic will benefit the plants. If you have a cheap source use it. If you are suggesting paying high prices for fish blood – don’t do it.