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How do you make homemade Fish/Seaweed Emulsion?

10 years ago


As you may know fish emulsion, fish meal, seaweed/kelp meal, and liquid seaweed/kelp are some of the most powerful natural fertilizers and soil amendments in the world.

NOTE: For those organic gardeners who prefer vegetarian soil amendments, you can skip the fishy ingredients, it's not necessary. There is plenty of NPK in alfalfa meal and other grains that you can use.

Most commercial fish emulsions are rated NPK = 5-1-1.
Most commercial liquid seaweed sprays are rated NPK = 0-0-1.

Even though these NPK ratings to a novice may seem low, there are lots of important trace elements, growth hormones, disease control, and organic matter in these products.

Fish Emulsion is mainly used for its quick high organic nitrogen and available soluble P and K benefits as a foliar feed. Fish Meal is mainly a great soil conditioner and great bacterial food to help feed the soil microherd. Even though there may be 4-5% organic N, 1% soluble P, and 1% soluble K in fish emulsion, there may be up to 6-8% total N, and 2-3% total insoluble P or K in it, that gets broken down later by the soil microherd. Most commercial fish products are made from the trash products of the menhaden fish. This fish is a relative of the herring, sardine, and anchovy fishes. Most commercial fish emulsions contain up to 5% sulfuric acid in order to preserve the fertilizer on the shelf, but also it supplies needed sulfur to the plant and soil. Most economical fish products do not contain any fish oils in it, which supply extra beneficial soil fungi. Most also do not contain much fish bones which supply extra calcium.

Seaweed/Kelp has a low NPK = 0-0-1. However, just like the fish products and all other natural fertilizers, there are more insoluble NPK nutrients and other trace elements in the product than meets the eyes. There may be up to 1-3% total N, 1-2% total insoluble P, 3-5% total insoluble K in seaweed products. The real benefit of seaweed is not in its NPK amounts. Seaweed/kelp can contain 60 trace elements, many growth hormones, and disease control properties in it! Basically every nutrient that any surface plant can ever need! If seaweed products are mixed with high N products like fish, you have an excellent complete natural fertilizer and soil amendment that will supply every NPK and trace element need of the soil and plant. Seaweed and other algae plants are some of the most powerful plants on earth, or should I say in the ocean. Seaweed is also an excellent food source for beneficial fungi in the soil.


A. It's cheaper to make most natural fertilizers and soil amendments in large quantities.

B. There are some nutrients that you get from homemade versions that are not in most commercial brands. For example, commercial fish emulsion since it is processed from trash fish, will have less fish oil, fish bones, and proteins than fresh fish parts or canned fish in a homemade brew.

C. Aerobic bacteria and fungi are essential to hot composting, disease control, and soil health. In commercial fish emulusions there no little to no aerobic bacteria in the containers. If there were any growing and living in the containers, the bottles would explode on the shelves! Homemade brews always will contain more beneficial microherd than most commercial brands.


You can use the following suggestions to the other suggestions in the Organic Gardening forum FAQ's on Compost Tea recipes when you brew these fish/seaweed foliar sprays or soil drenches.

You can use fresh fish parts or any cheap canned fish. The juices, sauces, or oils in the can can be used to breed beneficial microbes and supply extra proteins in the tea, so use it.

(NOTE: If you use canned fish products, you may want to let it decompose mixed with some finished compost, good garden soil, etc. in a separate closeable container for a few days before using. Since most canned meat products contain preservatives, this will guarantee that the good microbes in the tea will not be killed off or harmed in brew making.)

You can use any fresh or dried seaweed. Fresh seaweed has more N in it, but that really isn't important for seaweed teas. You can buy fresh or dried seaweed at most oriental grocery stores. Seaweed decomposes better if chopped up or liquified first in water before brewing.

If you are using fresh fish, you need to compost it separately in a 5 gallon closeable bucket. Fill bucket 1/2 full with extra browns like sawdust, leaves, or straw. You can add molasses to the fishy mixture in order to build up microbes in order to speed up decomposition. The sugars will also help control odors too. Open the bucket and stir the fishy paste daily or every other day in order to get air in the mix for better decomposition and better aerobic microbial growth in the emulsion. Let this paste rot for at least 1-2 weeks. The browns help control offensive odors and absorb organic nitrogen from the fish so that it is not leached out or evaporated.

Since commercial fish emulsions contain sulfur in the form of sulfuric acid, if you like you could add 1-2 tblsp of Epsom salt to the mix for extra magnesium and sulfur. Or to mimic the acidity of sulfuric acid and add extra trace elements you could add 1-2 tblsp of apple cider vinegar to the mix. NOTE: Recent studies have shown that unsulfured molasses or dry molasses powder is best for faster microbial growth in tea brewing.

You can now safely take the decomposed fish paste from the 5 gallon bucket and add it to your regular hot composting piles or add it to your special compost tea recipes. The more vegetable or fruity organic matter that you add to fishy compost the better you remove the offensive smells and the more trace elements you add to your compost and teas. This of course is optional.

You can add molasses or brown sugar to your teas also. Sugars are high carbon substances that not only can cause speedy microbial growth, but also sugars are an excellent natural deodorizer.

At this point you may want to decide whether you want to make a simple tea or an aerobic aerated tea for your needs.

When you make fishy tea, you need to add the seaweed at brewing time. Let it brew for at least 1 week, stirring every few days. If you decide to brew it aerobically with an air pump, try up to 3 days, or until the brew has a "yeasty" smell, or has a foamy top layer on the tea.

You can apply this fish/seaweed emulsion at a dilution rate from 1:1 to 1:5 ratio (5 gallons of tea to 25 gallons of water).

If you like, you can add a few drops of mild liquid soap per gallon as a wetting agent to get better coverage as a foliar feed at application time. (NOTE: If you are concerrned that using soaps may harm the beneficial microbes in your teas, you may want to just use liquid molasses, dry molasses powder, fish oil, or yucca extract as a spreader-sticker.)

You can use this tea as a foliar feed or as a soil drench or both. Soil drenches are best for building up the soil microbial activities and supplying lots of beneficial soluble NPK to the plant's root system and the topsoil texture. Foliar feeds are best for quick fixes of trace elements and small portions of other soluble nutrients into the plant through its leaves. Foliar feeds are also good for plant disease control. Foliar feeds work best when used with soil drenches or with lots of organic mulches around plants. You can poke holes in the soil around crop roots with your spade fork, to get more oxygen in the soil to further increase organic matter decomposition and increase microbial activity in the soil.

Remember all your homemade fertilizers and soil amendments can be as diverse and unique as you are. So have fun and keep composting!

Happy Gardening!