Fish Fertiliser Recipe

Following is a description of the difference between Fish Emulsion and Fish Hydrolysate and the Koanga recipes for making either a small or larger amount depending on the size of your garden.

This is one of our strategies for building soil and growing nutrient dense food without industrial fertilizer. We have a set of strategies including

  1. Growing and using  ramial wood chip
  2. Compost (made in very specific ways so we are not just recycling the deficiencies we already have) 
  3. Fish Hydrolysate
  4. Other Liquid ferts
  5. Biofert
  6. Vermicast
  7. Chicken compost with chicken on Autumn leaves or ramial wood chip

We use all of these strategies, however we expect most people will use those that suit them best for whatever reason

Fish Emulsion

Fish emulsion fertilizer is made several different ways depending on who is making it. The important thing to know is that fish emulsion goes through two stages of processing. The first stage breaks down the fish parts using enzymes, proteases, or chemicals. Then, and this is the important part, heat is used to break it down further and allow oils and other things like amino acids to be more easily removed. It’s this second stage of processing that makes fish emulsion less advantageous than fish hydrolysate. Fish emulsion fertilizer lacks many oils and proteins that fish hydrolysate fertilizer has in abundance. So let’s look at that!

Fish Hydrolysate

Fish hydrolysate fertilizer generally starts out the same way as fish emulsion. It gets broken down using enzymes, proteases, or chemicals. However, fish hydrolysate doesn’t undergo the heating and skimming process that you get with the fish emulsion. The higher quality fish hydrolysates only undergo “cold-processing” which just means they are never heated enough to break down significant amino acid chains. Good fish hydrolysate also retains the fats and oils that microbes love!

Koanga Fish Hydrolysate  Recipe

This method of making fish fertilizer is awesome because it is a cold process, chemical-free, completely organic way to make fish fertilizer right at home. While fish emulsion lacks beneficial ingredients vital to the final product, this fish hydrolysate recipe preserves all those active ingredients. You don’t want to miss out on those oils that microbes love. 

How to make your own Fish Hydrolysate :

This recipe  will make a few litres of fish hydrolysate, our larger volume recipe follows this one 

  1. Buy/catch  a fish.

TIP: Any kind of fish will work.  In fact, you might as well use trash fish, or fish discards like fish heads, guts, etc.  I like to use whole fishes though as I think that makes for a better product.

  1. Now, ideally you would throw the fish into a blender to mash it up into little pieces. Cutting it up first will help, and you may prefer to have a separate old blender for the job.   Remember, the finer the fish bits, the more effective the fermentation.
  2. Add water.  You can use a simple guide of 3:1 – 3 parts water to 1 part ferment material.  1 roughly 8 inch fish comes to about 500mL when ground up, so I add about 1500mL water.

TIP: ALWAYS USE NON-CHLORINATED WATER.  Chlorine kills microbes. Leaving chlorinated water to sit overnight doesn't release the chlorine these days as it used to. You will need to find unchlorinated water. 

If you are using a blender, blend up the mixture.  The water helps keep it loose so it blends much better after you add the water.

  1. Add lacto bacilli ( whey) to blended fish mixture.  I use 2tbsp per L.  You can use more or less if you want.  2tbsp/L is plenty though. Add 1/3 parts sugar.  This should be 1/3 the amount of fish you’ve added.  Sugar will be either molasses or some kind of unrefined sugar such as coconut sugar, rapadura etc cane sugar. (The sugar or molasses is basically a source of carbon which helps to hold the nutrients and stop them washing away or burning up the carbon in the soil once applied)

TIP:  Try not to use white  sugar since it is chemically bleached.   Just use whatever is cheap.  Glucose gives microbes energy.  Whatever you have access to cheaply, go for it.

  1. If using sugar, the equivalency is about 1KG sugar = 1L solution.  So if you have 500mL of fish , you want 1/3 of that in sugar.  You’d use about 167g sugar, or roughly ¾ cup.
  2. Blend the whole mixture up a bit.  It’s good to have it as fine as possible.
  3. Up to you how much you blend it, I blend until I don’t hear so many bones crunching in the blades of the blender.
  4. Now you have liquefied fish, sugar, and lacto.  Pour this mixture into a container.  Loosely cover the container.  No need to seal, because the container will explode as CO2 is released by fermentation.  You just want to make sure other things don’t get into it.  I use a container with a lid and loosely screw the cap on top (just make sure you don’t seal it because it WILL explode).
  5. The process takes anywhere from 3 weeks to over a month.  How do you know it’s finished?  By the smell.
  6. You know when it’s done when there is no smell anymore.  During fermentation there is a nasty smell, but once completed, there will be almost no odor.  You can open it, and put your nose right up to it.  Take a whiff.  Nothing but a faint vinegar smell.  Now you know its done.  Congratulations!  You’ve made your own Fish Hydrolysate! Transfer it to a smaller container, usually just a smaller water bottle, just for convenience.  At this time, use a strainer and a funnel to strain the bones and scales out of the hydrolysate.  But don’t expect a lot.  From a whole 8-10in tilapia, you will only get a little tiny pile of bones/scales.  They will feel kind of rubbery, not brittle.  Throw these in the compost pile or garden, they are excellent fertilizer and microbe food, already inoculated with microbes!
  7. Leave the cap on the strained concoction loose until you see no more little bubbles forming.  Then cap it and store it for use as your own natural fertilizer.

How to use this fish fertilizer:

Mix 10 mls per litre or 100:1 for larger amounts. Ie 100 mls in a 10 liter back pack sprayer, or watering can or venturi system via a garden hose


  • Use as a soil drench as opposed to foliar spray.
  • Inoculate compost to boost fungal population.  This is huge – major growth booster of fungus.
  • Use in compost teas to boost fungal growth, add Nitrogen.  Use at ¼ strength for this application(1/2 tbsp per gal).
  • Mix in water when watering plants, as a natural fish fertilizer and to enhance populations of microorganisms in the soil

200 Litres at a Time!

 We make it in 200 ltr barrels, and the recipe then following the same principles is

40 liters of fish put through the garden chipper

160 lt of spring water

13 liters of molasses( this is the only brought in ingredient, which we feel uncomfortable about so we’re looking at other options, traditionally soot was used!)

2 litres of whey 

Follow everything as above. When  making it in a 200 liter barrel put a tap into the barrel, a 300mm tap is best, 30cm above the bottom of the barrel so it never blocks up when extracting the fertilizer. 


General Liquid Fertiliser

Substitute 40 litres of fish meal, or ground fish, for 40 litres of seaweed, or cow manure, or comfrey, or a mix of any of these and follow the rest of the recipe, to ensure once again the nutrients are not water soluble and will not wash away and or unlock the carbon in the soil upon application.