Fertilizers Gardening Organic Gardening

Hydrolyzed Fish: Not Dad’s Fish Emulsion

Acadie Hydrolyzed Fish - 3 sizes

They say you learn something new every day. I certainly do. In fact, I learn quite a few things every day. Like, a few weeks ago, the difference between hydrolyzed fish and fish emulsion, two fish-based fertilizers.

A Fishy History

My dad, a serious gardener, was very fond of fish emulsion and used it liberally in our home vegetable garden when I was a kid. It’s pretty much a complete fertilizer, with all the elements plants need for their growth, and my father was convinced it was absolutely the best thing for vegetables. And he was probably right. In fact, had they been available to us in any quantity, I’m sure Dad would have buried fish in the garden!

But fish emulsion stinks. Sorry to say that, but it really does smell of rotting fish. And so did our garden. It would smell of fish for 2 or 3 days after each application of fish emulsion. And it often attracted the neighborhood cats!

As a result, unlike my dad, I’ve never been one for fish emulsion. I instead have been using another sea product, seaweed fertilizer, as a supplemental fertilizer in gardening. After all, it too is natural, rich in minerals and most importantly, like fish emulsion, contains all the trace elements (minor minerals) that plants need for their growth, making it the perfect product to prevent or correct nutrient deficiencies in plants. And there’s no bad smell to put up with.

Winds of Change

But I didn’t realize that the situation had changed.

Acadie Fresh Seaweed and Hydrolyzed Fish

It was only a few weeks ago, as I was talking with Christine Dionne, from Acti-Sol, a Quebec company mainly known for the hen manure fertilizers that I’ve been using for 25 years, that I learned that there is another form of fish fertilizer that doesn’t smell bad: hydrolyzed fish, also called fish hydrolysate. Acti-Sol recently picked up a line of fertilizers, Acadie, mostly seaweed fertilizers, but also hydrolyzed fish. It turns out this product been around for a long time: it’s just that I had never noticed it!

True enough, that means yet another barbaric garden term—hydrolyzed—I have to memorize … and it seems to me that my brain is a bit slower on the uptake than than it used to be, but I can adapt to that. And the product is actually quite different from the fish emulsion my dad loved so much.

Here is what I learned from Christine:

Hydrolyzed Fish Versus Fish Emulsion

Hydrolyzed fish is prepared from fresh residues of several species of deep-water fish (what remains after removing fish filets for human consumption, including the guts, bones, cartilage, scales and any remaining flesh), plus any bycatch. Ideally, several different species are used, because each species has a different nutrient analysis profile. It is simply put into water and ground up finely. 

Acadie Fresh Seaweed and Hydrolyzed Fish

Hydrolyzed fish is made from fresh fish harvested the same day, broken down by natural enzymes, then stabilized, which explains the lack of odor, as fresh fish doesn’t smell bad.

Since it is cold processed, it retains pretty much all of its attributes: not just minerals, but vitamins, amino acids, enzymes, and growth hormones all of which can be helpful for optimal plant growth. 

Fish emulsion, on the other hand, is prepared by cooking. That way, there is no rush to prepare it and is usually made from several days’ old fish and fish parts that have started to stink. And boiling results in a net loss of some of the components. It’s like eating raw vegetables versus eating cooked vegetables: more elements are retained when the product has not been modified by heat.

Also, one reason fish emulsion is boiled is so that the oil can be removed and used for other purposes, removing omega 3 fatty acids … and the efficacy of the product. Likewise, fishmeal, including much of the protein normally found in fish, is also removed, resulting in even more loss of minerals. The result is that fish emulsion is a sort of denatured, less effective version of the original fish.

All that is removed from hydrolyzed fish, on the other hand, are pieces of bone that couldn’t be ground up finely enough, and that is done simply by filtering. The result is that it is a more complete fertilizer than fish emulsion.

Hydrolyzed fish is easy to apply because it’s a liquid, with the consistency of chocolate milk (and, by the way, the same coloring as chocolate milk!). It can be applied by watering it into the soil or as a foliar spray. It’s so fine that there is no risk of clogging the sprayer. The same can’t be said for fish emulsion. With its thick consistency, closer to that of molasses than milk, it readily clogs sprayers and can only be used as a foliar spray with great difficulty.

Note too that many hydrolyzed fish fertilizers are certified for organic farming. The Acadie version, for example, is certified by Ecocert Canada and Quebec Vrai (OCQV).

The Other Advantages of Hydrolyzed Fish:

Christine told me about some of the other advantage of hydrolyzed fish:

  • It quickly corrects nutrient deficiencies;
  • It encourages the proliferation of bacteria that are beneficial to the ecosystem;
  • It stimulates rooting and flowering;
  • It nourishes the soil with its rich nutrients;
  • It increases the Brix (amount of sugar) in fruits and vegetables;
  • It’s the perfect complement to seaweed fertilizer, being rich in nitrogen and phosphorus while seaweed fertilizer supplies potassium. Thus, it can be practical to alternate between the two over the summer to reach a good balance in your fertilization.

My Experiments

I’m a rank beginner when it comes to hydrolyzed fish, my experiments only date back a few weeks, but … so far so good! 

Applying hydrolyzed fish to a watering can.

I first tried applying it as a foliar fertilizer to my vegetable and flower seedlings, bravely spraying it indoors (I would never have sprayed fish emulsion indoors: what a stink that would have made!). And I was due to fertilize my houseplants, so instead of seaweed fertilizer, I “fed” them hydrolyzed fish, this time watering it in. 

The fertilizer certainly passed the smell test. My wife, whose sense of smell, especially when it comes to my experimenting with new garden products, is about 15 times more acute than mine, didn’t even notice!

Applying it was simple enough. Just shake the bottle well to mix it and apply 10 ml (2 teaspoons) per liter (4 cups) of water, whether you water it in or use it as a foliar fertilizer.

The recommendation application is every 2 to 4 weeks; possibly more often when you use it as a foliar spray. Logically, you’d alternate between using it and a seaweed fertilizer, as mentioned above, for a proper balance between nitrogen and phosphorus (from hydrolyzed fish) and potassium (from seaweed).

During the summer, I plan to use it on my outdoor vegetables and herbs to supplement the slow-release fertilizer (hen manure) that I always apply as I sow seeds or plant out flowers and vegetables.

One warning: once mixed with water, hydrolysate can’t be stored. So, only prepare enough product for your current application.

Helpful Tip: Don’t leave hydrolyzed fish sitting around on the kitchen counter, otherwise someone in the family might mistake it for chocolate milk … and, although I haven’t tasted it, I’m pretty sure it tastes nothing like chocolate!

In short, hydrolyzed fish has completely changed my attitude towards fish fertilizer, which my dad loved so dearly. After all, I can now get all the benefits of fish, but without the smell! And I’m sure my dad would have been proud of my reconciling with fish fertilizer again!

*By Larry Hodgson in partnership with Acti-Sol.

Larry Hodgson is one of Canada’s best-known garden communicators. He has notably been editor-in-chief of HousePlant Magazine, Fleurs, Plantes et Jardins, À Fleur de Pot and Houseplant Forum magazines and is currently the garden correspondent for Le Soleil and radio garden commentator for CKIA-FM Radio. He has written for many garden publications in both the United States and Canada, including Canadian Gardening, Harrowsmith, Horticulture, Fine Gardening and Organic Gardening. He also speaks frequently to horticultural groups throughout Canada and the U.S. His book credits include The Garden Lover’s Guide to Canada, Complete Guide to Houseplants, Making the Most of Shade, Perennials for Every Purpose, Annuals for Every Purpose, and Houseplants for Dummies, as well as nearly 60 other titles in English and French. He is a past president of the Garden Writers Association (now Garden Communicators International) and the winner of the prestigious 2006 Garden Media Promoter Award offered by the Perennial Plant Association. He resides in Quebec City, Quebec, Canada.

4 comments on “Hydrolyzed Fish: Not Dad’s Fish Emulsion

  1. Christine Lemieux

    Good to know. Thanks!

  2. “Hydrolyzed Fish is made from fresh fish harvested the same day.” Do you mean that this fish is purposely harvested to make Hydrolyzed Fish fertilizer, or is it the by product of fish harvested for human food purposes, as is Fish Emulsion?

    Is there any scientific proof that the “vitamins, amino acids, enzymes and growth hormones in fish are directly utilizable by plants? My impression is that all organic materials need to be broken down into their inorganic constituents before plants can utilize them, in which case, the plant wouldn’t be able to tell the difference between Fish Emulsion and Hydrolyzed Fish.

    Can you also explain what you mean when you say that in the making of Hydrolyzed Fish fertilizer, the fish product is “broken down by natural enzymes, then stabilized.” It’s my understanding that “hydrolyzed” is a broad term meaning that molecules of water are added to a chemical structure, and that often, this addition is solely a mechanical addition, with no chemical bonding between the water and the molecules. Can you explain any details of this process?

    Aren’t the “Other Advantages” you list not advantages over Fish Emulsion, but rather advantages that both Hydrolyzed Fish and Fish Emulsion enjoy over other plant fertilizers?

    Thank you for this information.

    • Here is the answer I received from the supplier:

      We use the Fish after the fillet has been removed for human consumption.

      60-70% is leftover, after filleting. This was getting wasted, before we turned it into fertilizer.

      Hydrolyzed means that solids are broken down into a liquid, with enzymes. Enzymes are naturally in Fish.

      Emulsions are cooked, and ours is a cold process. A lot the benefits of our Fish, are cooked out or removed from the Fish Emulsions. We also don’t remove the oils.

      I am unaware of any university studies, on breakdown and utilization. The proof is in the product though, so maybe offer him a free sample.

  3. It sounds like something that was made from fish that got wet. hmmm.

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