Fish Fertilizer PreparationThis week in the Flog:

Making Fish Fertilizer Photos to go with the recipe!

Some time ago I finally ran out of the fish fertilizer I made last year. Time for a new batch! I documented the process for all those interested in seeing this awesome recipe in action!

Homemade fish fertilizer is an organic fertilizing solution that allows you to move away from petroleum-based commercial fertilizer. It is made from fish which is one of the very best sources of macro- and micro-nutrients for healthy growing plants. You can make it yourself with very limited resources. And it is SCENTLESS. We have an awesome recipe on how to make it here.

In my current living situation, I don’t have the time or space to get a good source of fish waste and make the recipe that way, so I’m just buying a tilapia from the market to use. It’s a nice size fish, and using the whole fish means the end product will be that much better:

Whole tilapia from the market, guts included.

Now the bloody work. I’m chopping the fish up into smaller pieces and then into the blender they go. This is a pretty messy process and I would encourage you to do it *outside*.

The fish gets chopped up and added to the blender

Now before I blend up the fish, I’m going to add the water and sugar. The fish is a little thick to blend on it’s own so I add the water before blending – and adding the sugar now allows the blending to help dissolve it. I’m adding 1L of water, a little less than what our recipe calls for but no matter, there is no real right or wrong here. I’m also adding 150g of sugar – 1/3rd part sugar to tilapia.

We add the water and sugar before blending to make the blending step easier

Now this whole mixture gets blended up really well. Only takes about 5 minutes or so of blending/pureeing.. My cheap blender has a little trouble with the bones at first but after awhile it’s pretty well blended. Check out the blended goop:

After blending, the fish fertilizer is very thick and uniform in color

Last step – add the lacto. I’m adding 2 tbsp of dilute lacto serum – there is no rule here, I could have added more or less no problem. But 2 tbsp for this amount of mix is about right in my book, maybe a little on the heavy side which I like.

Now I just blended it enough to get the lacto mixed well, and then this goes into the fermentation vessel. In classic Gentry style this is a plastic juice jug. Your fermentation vessel doesn’t need to be anything special as you can see from mine, haha. But it should keep the liquid as anaerobic as possible. For most people this means installing an airlock in the container. An airlock, used in wine and beer production, allows air out but not in, keeping the inside oxygen-free.

Fish fermenting away in my homemade fermentation chamber

Whoa! What is that blue tube with the hose going into it?! It’s a homemade carbon filter I added to the system. It’s not 100% functional for what I want from it, but it does cut the smell completely. I know a number of people complained about the smell during fermentation. I’ll post another article on how to make your own carbon filter, then you don’t have to worry about the smell anymore. This also works well as an airlock.

If you’re curious about how fermentation is going, watch your airlock for bubbling. In my case my airlock is the carbon filter with the little outlet tube. So for me to see, I dip the end of the tube in some water. And what do you know – bubbling away! This indicates CO2 and other gases are being released through the process of fermentation, and is a great sign of a successful fish fertilizer production.

It’s easy to tell if your fermentation is going – just watch for air coming out. In an airlock watch for bubbles – in this system I dip the end of the tube in water to check for bubbling.

Now let’s skip to the end of fermentation to see the good stuff – final product! Fast forward 3 weeks. In the warm weather of the tropics here in the Philippines, this is more than enough time to complete fermentation. To bottle up my fish fertilizer, I’ll use a strainer and funnel, and pour it out of the jug right into the storage container.

After fermentation is complete, I strain the liquid to avoid getting chunks in my fertilizer

Here’s the great thing, it’s SCENTLESS. Very nearly anyway, and the smell it does have is like wine, like a fruit wine or something, it’s wonderful. I mean wonderful compared to how it smelled going in. Fermentation really does some cool stuff. Who would have thought a rotten fish could have no smell.

Another cool thing, what’s left in the strainer! We started out with a nearly 1 lb fish. Scales, gills, bones, skull, everything went into the brew. It was blended initially and that helped dramatically to break up those big bones and increase surface area for microbes to work on. But there were still a lot of large bones at that stage. Now look at what’s left in the strainer after I’ve emptied the jug:

There is very little solids leftover after fermentation – the fish was digested almost completely during fermentation

Amazing! Around 2 tbsp worth? Tiny! Out of that whole big fat tilapia, we end up with a little tiny pile of bones. And they are different. They aren’t brittle, they are soft and rubbery. They are clearly degraded, and will break down in the soil in no time. I added these directly to one of the planters.

And now you can see the fish fertilizer in it’s final jugs – more recycled plastic containers. I ended up with about 1.5L of fish fertilizer from that fermentation. This will be great for my plants, they need a bit of a nitrogen boost.

The final product from this fermentation is 1.5L of fish fertilizer. I have it split into 1L and 500ml bottles.

Pretty cool stuff. It is really fun making your own fertilizer and seeing how fermentation produces such dramatic results.

I use this fish fertilizer in many applications:

• 2-4tbsp/gal in water for plants to green them up (normally just 2tbsp/gal but sometimes more)• 1tbsp/gal applied to the compost pile, nitrogen boost and microbe feed• 1-2tsp/gal in aerobic compost tea (very small amount as the oil tends to reduce aeration)• 2-4tbsp/gal in anaerobic compost tea (or even more, there is no limit here)• 0.5tbsp/gal in water to moisten animal feed bokashi prior to feeding worms/roaches/dog

There are all kinds of applications for this stuff as you can see in the list above. It is not only amazing as a direct fertilizer, but also as a microbe food source, nutrient source for large animals, and more. Get creative and play with it around your house. It is awesome stuff!

Keep on growing.

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March 18th, 2014 | Patrick | Category: DIY, fish fertilizer, Homemade Fertilizer, How To, Recipes, Urban Gardening

Linda

March 19, 2014 at 7:18 am - Reply...

Can’t wait to try this. I need to wait a week for my lacto to be complete. It could be good also to wait for the carbon filter instructions so I don’t alienate my family!

o Patrick

March 23, 2014 at 9:52 pm - Reply...

Haha yeah, you know I never noticed a big smell during fermentation, but some people have complained about it. There is definitely a smell during fermentation, which dies when fermentation ends, it’s pretty neat. But anyway I’ll post the method on how to make the carbon filter soon, it’s simple and effective.

Cheers,Patrick

David Di Cecca

March 23, 2014 at 1:07 pm - Reply...

Is Whey powder an equivalent to Lacto serum? And if so how much powder would I use.

o Patrick

March 23, 2014 at 9:41 pm - Reply...

Hi David,

Whey powder, as in the protein powder? No, that is a different thing. To make lacto, follow our recipe on making your own lacto serum.

Cheers,Patrick

Marion

April 4, 2014 at 5:06 pm - Reply...

I make milk Kefir which is fermented milk, could the Whey strained from thiswhich has a wide variety of Lacto bacillus organisms be used as a substitute.

o Patrick

April 10, 2014 at 2:06 am - Reply...

Definitely! Would be awesome!

Daniel

April 17, 2014 at 7:36 pm - Reply...

Hi Patrick,

I’ve been fermenting my fish for about a month now. Most of it has broken down but there still are some chunks and smell that resembles death but not nearly as bad as it was the first couple of weeks. There is separation of the oil and the liquid is almost an orange color. I noticed yours was more of a brown color. I just wanted to know if that sounds about right? We have cold weather at night and I don’t have the ability to blend the fish so I’m hoping that may be why its taking its time even though I did chop the fish into small pieces…

o Patrick

May 6, 2014 at 11:37 pm - Reply...

yep, that’s all fine. it will separate into layers if you let it sit, due to the oils. I need to add a picture of that.

If you want to ferment more, just add more sugar and water. Help reduce the amount of chunks in your mix.

Cheers,Patrick

Ryan

May 1, 2014 at 10:42 am - Reply...

HI Gil and Patrick,

Any idea what the NPK values of this stuff might be? I’d like to go organic at our small hops farm and have unlimited access to fish. Hops need about 160lbs N/ ac. but not sure how you might gallons/ acre required at 2 tbsp/gal dilution. Thanks for the help and what a great site! Ryan

o Patrick

May 6, 2014 at 11:16 pm - Reply...

Hi Ryan – it really depends on what fish you use, how much water you add initially, etc. But they are low in inorganic Nitrogen. You would want to still use an organic fertilizer in conjunction with these, INITIALLY. Once you convert to organic and practice composting, green manure, cover cropping, etc, these will be excellent and adequate sources of Nitrogen. But it’s a process, and takes some time to match inorganic inputs. I don’t want to discourage you but as a commercial operation, I don’t want you to lose income.

Ryan

May 8, 2014 at 5:41 am - Reply...

HI Patrick,

Thanks for the response. I’m not at all discouraged. I think this will be a great addition on our farm, once I get it figured out. I just finished mixing 500 gallons of this stuff yesterday. It’s smelt season up here and I’m brewing it in 55 gallon barrels. It’s a bit cold up here so hopefully, things will progress (albeit slowly). Everything else has gone organic but I haven’t been able to find a suitable (affordable) organic fertilizer. We’re already using composed cow manure and white clover for cover and would love to be done with the Jack’s 20-20-20 at some point. Our farm is on a trout stream so I need to be careful with the fertilizer inputs even if it means coming up a little short in lbs N/ ac.

Thanks again,

Ryan

Patrick

May 8, 2014 at 7:39 pm - Reply...

Ryan,

Sounds like you are taking environmental stewardship seriously, that is awesome to see. We need more people like you, and it’s one of the major themes of this site though I haven’t focused on it much since I’m busy enough covering the recipes and organic topics.

Also looks like you’re well on your way to being full organic. The composted manure and cover crops should pay off after a few years – takes time to build up organic matter in the soil. Have you used biochar? Check out our page on biochar – I highly recommend it for increasing efficacy of inputs, organic and not. That also takes a few years to become fully effective, but the results in studies have been awesome.

Cheers,Patrick

George

May 8, 2014 at 11:29 pm - Reply...

Hi Gil and Patric!I am very excited with your website it is full of useful and practical information. I did the fish hydrolysate recipe but used live yoghurt whey instead of the suggested lacto-fermented serum. I let it ferment for 2 months (it’s still kind of cold here in Athens Greece, around 19 degrees Celcius, especially at nights) and finaly I got a mix of orange and gray colored liquid that smells “fish” and a little vinegar, not bad, not rotten, just “fishy”. Of course next time I will use the rice-wash serum that I already have brewing, but do you think this one is still good to use for my garden? I ask that because in your recipe you say it should almost have not any smell.Thanks,George

o Patrick

May 12, 2014 at 8:37 pm - Reply...

Hey George,

Yep, that will be awesome for your garden, no worries. Yeah, depending on the fish used and such, there might be a little smell. But it should have a touch of alcohol or vinegar to the smell, like you observed, and it shouldn’t be foul or putrid. I think you’re on the right track and made a great batch.

Cheers,Patrick

George

June 12, 2014 at 12:24 pm - Reply...

Thank you Patrick for your response.To all people wandering if yoghurt whey can do the trick with fish hydrolysate, I have an answer!Yes, it worked for me. I used the amount stated in this recipe, but instead of rice-wash fermented lacto serum (which I had difficulties making it), I used fresh, homemade (greek) yoghurt whey. I made a couple of batches this way and I’m already using it regularly during watering on my vegetable garden and fruit trees with very positive results. I can’t wait to taste the first tomatoes or peppers of the season!The way to get whey is to get some un-strained yoghurt and simply strain it in a container using a sieve and a piece of cloth. Put it in the refrigerator and after about 5 hours it’s fully strained. Use the liquid as lacto serum substitude. It can also be used to ferment foods like vegetables, cereals, ketchup, etc. as a nutritional boost.Again, Thank you for this wonderful site!

George

Patrick

July 3, 2014 at 12:03 am - Reply...

Excellent feedback George, I love your improvisation! That’s a great contribution to the recipe, I might have to add an addendum section for these recipes, alternative ways to make them.

Cheers,Patrick

Taylor

May 12, 2014 at 11:58 am - Reply...

Patrick,Thank you so much for the information. I’m curious after fermentation is complete and you bottle your liquids is there any issue with expansion? Bluntly do your bottles explode or anything to that affect? I imagine if fermentation is completely done then no gasses would be emitted but I want to ask an expert .ThanksTaylor

o Patrick

May 12, 2014 at 8:56 pm - Reply...

Hey Taylor,

Great question, YES – quite often fermentation goes a bit longer after you transfer to bottles, and in that case you need to make sure to crack the lid to let the buildup out each day, or keep in airlock. When fermentation is completely done, yes there isn’t expansion anymore, but that’s hard to see sometimes, so you will no doubt run into this issue at some point. Better to be aware of it. Because the bottles will explode, it’s happened to me more than once haha. Have fun!

Cheers,Patrick

o gil carandang

June 26, 2014 at 2:53 pm - Reply...

in most instances, it may “explode”. this is normally because the fermentation process may not be fully completed yet and still lots of undigested protein. what i do to accelerate the process is through aeration. put a bubbler like aquarium aerator and after a while, the “undigested” protein shall be “combusted” and eventually shall stabilize. no more “explosions”!

Taylor

May 12, 2014 at 12:54 pm - Reply...

Patrick,Ugh more questions have arose: does the mixture need to be stirred throughout the fermentation process, and where can I find your link on how to make your own carbon filter?Thanks,Taylor

o Patrick

May 12, 2014 at 9:01 pm - Reply...

Hey Taylor,

No prob with the questions. You don’t need to stir during fermentation. I find that as long as you keep it anaerobic, stirring can help fermentation progress by mixing up all the ingredients again, but I wouldn’t remove the lid to stir or anything. Just keep the principles (anaerobic) in mind and you can do whatever within those bounds to help the process along.

I haven’t posted the method for the carbon filter yet but I will later on – it’s pretty handy for keeping the process scentless. In any case, I don’t find the smell during fermentation to be overwhelming, it leaks out the airlock fairly slowly especially for small batches.

Glad you’re having fun with the recipe, your plants will love it!

Cheers,Patrick

Taylor

May 14, 2014 at 11:59 am - Reply...

Patrick,Thank you for the information. Iv seen people run their airlock exit through a bucket of water. If no air bubbles come out does this mean that the fermentation is done or can expect that the process might restart, and create more fumes? Is there anyway to be certain that the fermentation is complete or anyway to stop the fermentation . Refrigeration? I live in a cold climate where my access to fish is at the end of the growing season and I want to save my fertilizer till the spring without fear of explosion over the 6 months. Harsh right? Also I wonder would it be as advantageous to fertilize during fall, end of growing season, rather then before or during growth.Thanks again for your spring of knowledge,Taylor

o Patrick

May 19, 2014 at 10:53 pm - Reply...

Hey Taylor,

Lots of questions there but I’ll try and answer them. Yes it can restart a bit after you transfer containers, so watch for that. You can refrigerate and that will SLOW fermentation but it wont stop it completely. Just crack the container every few days for the first while. Ideally you would just make the fish fertilizer, then leave it in airlock all winter. No need to transfer it, and the airlock will let air out as it needs to and keep it anarobic. You’ll want to fertilizer before and during growth. You can also fertilize during fall no prob, feed that nice winter cover crop to be turned in during spring.

Cheers,Patrick

George

May 20, 2014 at 11:33 pm - Reply...

Love this stuff, great informative article!

Taylor

May 30, 2014 at 12:01 pm - Reply...

Hi again Patrick,Just getting to final steps of my LAB. Nervous haha, but all looks well. The three layers you speak of are they as follows: top thin film, middle (most of the quantity) foggy, and bottom thick curdy looking stuff?

Do you dilute the final LAB before putting into the fish mixture? Or do you use pure?

If you were going to ferment fish in a 55 gallon container/quantity how much lacto would you use? Would you keep the same ratio as with smaller batches?Thanks again,Taylor

o Patrick

July 2, 2014 at 10:38 pm - Reply...

Hi Taylor,

Yeah that happens sometimes the curds sink, that’s ok. For your questions: Yes, dilute before adding to fish. For a 55 gallon drum of fish you would use the same rate as for smaller batches, although you could use less. I would just add a gallon of diluted serum. I just picked that number, it should be plenty, although at the rate recommended in the recipe it would be 6 L i think. Up to you how much you add.

cheers,patrick