Easy Homemade Fish Emulsion Fertilizer

I've read with much interest from the internet how folks prepare homemade fish emulsion and swear by its effectiveness. There are so many articles saying how simple the process is in making fish emulsion. I suspect though that many of these how-to articles just parrot each other.

There is little material thus far, however, by way of photos and/or videos that illustrate the processes involved in this so-called simple procedure - as of this writing, anyway. So this article will illustrate, by pictures, just that.

Simple and easy - yes - but a bit messy and stinky. You will not believe how bad the stink can be. And for many, that may be an understatement because the basic raw material for fish emulsion is well, raw fish scraps (as shown above) which will be decomposed.

Sources of Raw Fish Wastes or Scraps

You will likely be able to get fish scraps or wastes in places where fish is cleaned prior selling or consumption. The fish section of the wet market will usually have traders removing fish parts like intestines, gills, liver, gall bladder, heart, fins, tail, scales and even bones. Typically, these are thrown away and so you could just ask them for free.

That's how we get fish scraps for free. Many traders in the wet market are just happy to get rid of their refuse from the fish cleaning. We're able to get a kilo or so by just asking. Of course the fish scraps include everything and you just can't become picky and select a few parts. I bring along a plastic container with a lid on it. Plastic bags won't do because of the risk of them bursting open.

Making Your Own Fish Emulsion from Fish Scraps

The procedures outlined below will yield roughly 2 liters of concentrated fish emulsion from 2 kilograms of fish scraps. Because of fish scraps volume, it will take 1 month for it to sufficiently decompose and for you to extract the fish emulsion. Your mileage may vary. Obviously, a smaller amount of fish scraps will yield a smaller amount of fish emulsion and will take lesser time.

The pulp that will be left behind after extracting and collecting the fish emulsion is not wasted. It may be used as a good starter mix for the next batch of fish emulsion, because of its state of decomposition. It may also be used to feed a compost pile that can later be applied and mixed into your garden soil.

Do NOT use the extracted fish emulsion directly on your garden plants. Instead, dilute to apply the fish emulsion as fertilizer.

  • Raw Fish Scraps - 2 kilograms
  • Molasses - 1 cup
  • Sawdust - 2 lbs.
  • 5-Gallon Plastic Bucket with Cover
  • Window Screen, 18" x 18" - 1 pc.
  • Garden Hand Rake or Spatula

  1. Pour an inch-high layer of sawdust at the bottom of a 5-gallon bucket. This is the component in the mixture that absorbs extra nitrogen expelled by the decomposing fish. While others choose a variety of "browns" to be added like dried leaves, grass clippings, etc., I only put sawdust for consistency and to keep the entire process simple.

  2. Pour all the fish scraps in the bucket. If the fish scrap has water, pour that in as well.

  3. Put 2 tablespoons of molasses into the bucket. Molasses feeds the microbes that eventually decompose the fish parts. The sweet sugary smell of molasses does NOT remove the offensive odor of rotting fish, but simply masks it.

  4. Mix the fish scraps, sawdust and molasses thoroughly with a garden hand rake or spatula. The reddish brown color below comes from the sawdust. It may be a bit heavy to mix all together because much of the fish scraps is still semi-solid.

  5. After mixing thoroughly, sprinkle a thin layer of sawdust on top of the mixture as shown below.

  6. Be sure the layer of sawdust is spread all around. If the sawdust quickly absorbs the mixture water and becomes wet, continue adding additional layers until the topmost layer of sawdust appears dry.

    The layer of sawdust will minimize and contain much of the offensive odor of rotting fish inside the bucket.

  7. Cover the bucket with the window screen piece. Ensure the piece will sufficently cover the bucket's opening and will have a couple of inches extra beyond the bucket's rim. The window screen prevents adult flies from getting inside the bucket. If adult flies are allowed to get inside the bucket, you'll have a problem with maggots.

  8. Replace the bucket's cover and twist to secure the window screen in place. The window screen between the bucket and cover creates a space gap for air. It is NOT advisable to seal the cover because gases are formed during decomposition and need to escape.

    Optionally, add a heavy weight on top of the bucket cover to weigh it down. This will prevent the accidental bumping off the bucket's cover. The weight will also discourage pets and animals from knocking it off.

  9. Avoid opening the bucket anytime during the day for the next two weeks. Flies will almost immediately swarm towards the open bucket. If you need to open the bucket, do this at night.

    The photo below of 3 flies on the bucket cover and window screen shows how smelly the contents have become. This photo was taken during the first week at daytime.

  10. For the next four weeks, open the bucket every other day to mix and aerate the contents. The aeration discourages the buildup of anaerobic bacteria that contributes largely to the bad smell.

  11. Continue adding 2 tablespoons of molasses as needed to help control the odor and aid in the decomposition of the fish scraps. Note that fish bones, heads, fins and tail will take longer to decompose.

In the first week, the stench will be horrible. Try to do the mixing at night when there are no flies. If there is wind, turn your back to where the wind is coming from so you won't smell most of the wafting odor. In the second week, the odor will smell like that of fish sauce that's common to Thai and some Asian cooking.

By the third and fourth week, much of the contents would liquefy because of decomposition. Because of that, it becomes easier to mix the contents. The odor will be less offensive, but still bad, nonetheless. The mixture will also be a bit darker because of the added molasses.

After four weeks or roughly a month, you'll be ready to extract and collect the fish emulsion.

Instructional Video for Homemade Fish Emulsion Fertilizer

Other Articles in this Series:

Collect and Extract the Homemade Fish Emulsion
Apply Homemade Fish Emulsion Fertilizer to Your Garden

Go ahead, post your comment below!

corrine said...

So here is your fish emulsion recipe. Yuck!!! No wonder you have wonderful veggies! But no way Jose, I can't do this. What pains you are willing to make to grow those veggies. You must be amply rewarded with good harvest.
Hope you can have tips on how to control pests like aphids.

corrine said...

Oh wow! But isn't it scary that the manure may touch the leaves of like pechay and contaminate them? How :)

Blackdove said...

Hi Corrine. I don't grow only veggies. Ornamental plants and trees benefit from fish emulsion as well.

I'd be more scared to find chemical ferts and pesticides abundantly applied on veggies. For veggies, organic ferts is the safer way to go.

Anonymous said...

All sounds good EXCEPT avoid Molasses unless it is organic. Molasses is made from corn and 92% of corn products are GMO so they contain toxic GLYPHOSATE (Roundup)residues which are harmful to your health. Glyphosate is a neurotoxin and causes tumors....See gmoevidence.com Keep healthy!

drew p. said...

Only 7 percent of the molasses produced contains corn, from starch derived molasses. The majority is made from sugar cane 60% and sugar beets 32% and 1% from citrus. So it's highly unlikely that you will get Glyphosate from corn. See article


Unknown said...

Great article. How diluted should the final solution be in order to be poured in veggies?

Blackdove said...

Rodrigo, it's 1 tablespoon to 1 gallon of water. How to Apply Fish Emulsion.

Anonymous said...

I admit that I cheated. I bought a 32 oz bottle of Alaska fish mixture emulsion fertilizer from Wal-Mart for less than $6.00 and it was shipped for free because I had other things on my list. I have not even opened it yet, but it's not supposed to be too smelly (label says). Now I'm looking for the recipe posted before, for a gal. water, 1 tbsp fish emulsion fertilizer 1 tbsp Epson salts and I think 1 other thing??? Could it be molasses? I will try to let you know how it works.

Unknown said...

I know this may sound dumb but does the cover need to be tightly sealed? because I've tried your procedure already and after two weeks I looked into it and I was so worried to found a lot of maggots all over the bucket :( Though I did not use a window screen instead a mosquito net (because I have a lot of it and I don't want to spend much) because both are somehow similar. So, should I just a window screen then? I'm REALLY HOPING for a QUICK REPLY because this is for my study huhuhu so sorry for rushing you, plus, do you have any suggestions? I think I'm going to give it another try

Blackdove said...

No, it should NOT be tightly sealed. This is to allow gas to escape. But there should be NO OPENING for flies to get in, otherwise you will get maggots.

Unknown said...

I made my fish emulsion last March and it is now December but the fish emulsion still smells very bad and plenty of maggots too! Looking back, I admit I did not make much of the stirring since I covered it. What can I do with the smell and the maggots??

Blackdove said...

The maggots indicate that the container wasn't covered adequately. I admit maggots are a nuisance. I'd probably throw/ bury that batch in a pit. Then start over.

Unknown said...

My dad had the idea to put a u trap PVC pipe on the top of the bucket with a bit of water in it. The water blocks the smell and allows gas to get out. Also blocks flies and what not.

Unknown said...

My dad had the idea to put a u trap PVC pipe on the top of the bucket with a bit of water in it. The water blocks the smell and allows gas to get out. Also blocks flies and what not.

Arthur said...

Can I replace molasses with table sugar, saw dust with coffee grinds? Feel free to call me #CheapBastard because I am and using what I already have beats running out to get more stuff. I already got a garage full of more stuff :)

Anonymous said...

Hello! Can the fertilizer really not be useful anymore if there are maggots? Because I'm doing research but I can't really repeat and start the process over again. What effect does it have if there are or were maggots?

Kathleen R. said...

Appreciated this thread. Urban small & mostly containers-on-elevated-deck gardener here. Sub-urban setting still home to abundant deer, wild turkeys, the occasional fox, etc.
Interested in trying to decompose the fish leavings from our twice weekly pescian meals. Will try small batch today, keep it outside.
Given that there is no stair access (although tree near deck may offer access to small critters), can I expect critters to be attracted by the odor? Also, since I am starting very small (1-qt Ball-Mason jar), can abort the process entirely if our extremely high and windy location here still offends. TIA for the favor of a reply.

Unknown said...

Pode usar açúcar mascavo

Blackdove said...

I couldn't quite imagine how that pvc pipe setup is done, but great that it works for your dad!

Blackdove said...

Not sure about that, Arthur. I haven't tried table sugar to replace molasses. Yes, I believe you can replace saw dust with coffee grinds. Any powdery yard waste like dried leaves crumbs would work too.

Blackdove said...

Maggots. There's no really big issue if only for home-use. Of course, handling of fertilizer is quite bothersome.

Blackdove said...

Hello Kathleen R. Am not sure about the critters you speak of, but the odor can be quite strong. Try it out for a small batch first - that can be easily disposed if needed.

Unknown said...

Molasses is a liquid jeggory

Anonymous said...

Some misinformation here… which, when corrected, will make the process MUCH easier. The microbes doing the work are the anaerobic ones, so you don’t need to open and stir the smelly stuff. Instead, seal off the bucket (no need for window screen but you absolutely will need a water airlock (very cheap from brewing supplier, drill hole in your bucket cover and screw it in with rubber gasket so it’s airtight) then just leave it alone for a couple months. With your perfect seal you won’t be bothered by either smell or maggots. To jump start the process add some sauerkraut juice before closing your bucket, that is your microbial starter. Also use dechlorinated water (either water which has been boiled and cooled or just let to sit overnight).