How To Make Homemade Fish Fertilizer (DIY Guide) 

Homemade fish fertilizer is the perfect natural fertilizer for your gardening needs. Luckily, anyone can make a homemade fish fertilizer formula with three simple ingredients. 

Follow these easy steps to make a homemade fish fertilizer for your plants: 

  1. Gather your ingredients and a bucket for mixing. 
  2. Measure out your ingredients. 
  3. Mix your ingredients in the bowl.
  4. If desired, mix in extra organic additives. 
  5. Cover your bucket with a lid, but do not seal it all the way. 
  6. Let your fertilizer ferment. 
  7. Dilute your fertilizer. 
  8. Store the excess fertilizer in a safe place. 

As easy as making homemade fish emulsion can be, it’s always best to follow directions when attempting a new task. If you’d like more in-depth instructions that discuss the simple steps above in greater detail as well as some tips and tricks for enhancing your fish fertilizer, keep on reading. 

1. Gather Your Ingredients and a Bucket for Mixing

The first step is to gather a large and sturdy bucket that you can use to mix your fish fertilizer. 

If you can, find a bucket that can hold a few gallons. Ideally, you’ll need one that can accommodate roughly 3-5 gallons (11.3-19 liters) for easy handling and mixture. 

Once you have your bucket, gather the following ingredients: 

  • Fish 
  • Sawdust, leaves, or compost of some kind 
  • Blackstrap molasses 
  • Water 

When shopping for the necessary fish fertilizer ingredients, you can choose your preference of fish, compost, and molasses. Fish fertilizer does great with canned fish like sardines, and many choose to incorporate sawdust, compost and leaves altogether. 

It is best to determine which ingredients you need and how much of them before heading to the grocery store. Here is a list: 

  • Roughly 8 – 10 cans of herring fish. Mackerel or sardines are a great option, and they come in cans. Additionally, you will find oils and liquid residue that is perfect for adding to your fish fertilizer. Other fish options work well, too, if you would rather skip using herring fish. 
  • A large amount of aged compost, leaves, or sawdust. Preferably, all three. This option brings an earth-like texture to your fertilizer. Many use compost or sawdust alone, but combining all three can provide microbes and many different textures that enhance your fertilizer in the fermenting process. 
  • A decent sized bottle of blackstrap molasses. Although you will not use the entire bottle of molasses, it is good to have it handy. Having molasses for your fertilizer mix is important for the fermentation process. It adds sugars and minerals to your mixture. 
  • A measuring cup, if you do not own one already at home. This is important for measuring out your molasses. 
  • Water. Just if you need it. 

Every homemade fish fertilizer will vary here and there, but most homemade recipes follow an ingredient list similar to this for a spectacular turnout. 

2. Measure Out Your Ingredients

Now that you have your ingredients, it’s time to measure them correctly.  

Each ingredient can vary in size, depending on how much fish fertilizer you want to make. It is best to measure your ingredients beforehand to make it easier. 

The following measurements can vary but are recommended for a 3 – 5 gallon (11.3-19 liter) bucket of fish fertilizer. 

You can begin by measuring out your compost, sawdust, and leaves. Your compost is the primary ingredient of your fish fertilizer, and your bucket should be half full. Adding compost is recommended over just incorporating sawdust and leaves. 

If you purchased your fish in cans, no measurement is necessary. If not, the sizes of your fish should roughly measure out to be ⅓ of the compost. 

Your molasses is the final ingredient for adding in. You will need up to 3 tablespoons of molasses for every gallon of fertilizer you intend to make. You can add more or less, if you feel your mixture needs it. This may be especially true if the fertilizer batch you are making is on the larger side. 

Additionally, having plenty of water nearby to add to your mixture will be important as well. Using a hose is recommended. 

3. Mix Your Ingredients in the Bowl

Adding all of your ingredients into the bucket is step one towards making your fish fertilizer. Once this has been completed successfully, it’s time to mix it all together. 

When mixing your fertilizer, it may be best to do it outside. Fish fertilizer can be messy and tends to smell. You can also add a tarp underneath your bucket to protect it from spillage if needed. 

This step requires that you pour out the ingredients into your bucket full of compost, leaves, and sawdust so that the bucket is half full. If your bucket is on the smaller side, it’s best to measure accordingly. You may also need less fish and molasses, too. 

Afterward, you can fill it with water. It is best to stop at two to three inches (5 to 8 cm) from the top of the bucket. The fermentation process will do well with a small amount of air in the bucket. This is also so your fertilizer does not spill when the bucket is moved. 

Once your bucket is full, you can begin dumping in your fish and all the oils that come in the container (if using canned fish). If you’d like to dump your fish in before the water, that’s also okay. 

The final step is to add in your molasses. This ingredient is important for fish fertilizer. If you purchased a small bottle, you might want to add the entire thing, depending on how many gallons of fertilizer you have. 

4. If Desired, Add in Extra Organic Additives 

Fish fertilizer is full of simple ingredients that naturally help many plants. Although there is no need to add additional ingredients to your mixture, some gardeners and plant fanatics have found that it can be beneficial. 

It is recommended to try out a homemade fish fertilizer without additives on your plants before experimenting. Every plant has its own needs, and some plants do not do well with extra additives. 

Nevertheless, some additives provide benefits for your plant’s health. Here are a few to consider: 

  • Epsom salt. Although unnecessary, you may want to add Epsom salt into your fish fertilizer. This is helpful for plants that need higher amounts of N-P-K. Most fish fertilizers give plants a boost of nitrogen already, however. 
  • Additional types of compost. Although traditional compost, sawdust, and leaves are great options, individuals may want to add in other compost options as well. Farm manure and even vermicompost are an option.
  • Seaweed. Seaweed is a great additive to add to your fish fertilizer to calm down the odor that occurs during the fermentation process. It also provides additional minerals, nitrogen, and potassium. 

5. Cover With a Lid, But Do Not Seal It All the Way 

Fish fertilizer requires fermentation, which is the next step in the process. 

Once you have measured out and poured all of the ingredients into your bucket, you can mix them together. It is best to have your fertilizer mix smooth and distributed as evenly as possible. 

Next, it’s time to cover your bucket with a lid. If your bucket does not have a lid, finding some type of covering for your fish fertilizer is important. You can use any type of seal to close your bucket. 

If left open, bugs tend to swarm the bucket. Bugs can ruin your fish fertilizer and cause issues for your fermentation process. When closing your bucket up for fermentation, here are a few things to remember: 

  • Close your bucket with a lid, but do not seal it all the way. Sealing your bucket all of the way can create issues for the fertilization process. 
  • Poke holes in your coverage or find an alternative way for airflow. This is essential if you are utilizing a material like a piece of foil to cover your bucket. Covering it with something light on top is also an option for airflow, but there must not be room for bugs to crawl inside. 
  • Leave your bucket in a safe place. Your bucket should not be touched and should be left in a safe place after adding the ingredients in, so it can ferment. If used before fermentation occurs, it may ruin your plants or not work as well. 
  • Add a mesh material over the bucket with glue, even if applying a foil or another material to the top of the bucket. Bugs will find any way to get inside your fertilizer, especially maggots. This will ruin your fertilizer, as mentioned previously, and will create a huge mess. 

6. Let Your Fertilizer Ferment 

The most valuable part of fish fertilizer is the fermentation process. If your plants are fed fish fertilizer without fermentation, it won’t supply them with the proper nutrients that they need. 

Before setting your bucket aside, it is best to make sure all of your ingredients are properly mixed. This helps with the breakdown of ingredients while fermenting. It can take longer if this is not accomplished. 

Your fish fertilizer should ferment for two weeks at a minimum. It can take longer, and a month is recommended if you would like your formula to be rich in nitrogen. 

Before sealing the lid for fermentation, it is important to make sure you have everything in order. Here are a few suggestions: 

  • Confirm that every ingredient has been properly measured and mixed. Once your mixture begins to fertilize, new ingredients should not be added to your mixture. This will prolong the process. After your mix is finished fermenting, it will be ready to use. 
  • Cover your fish fertilizer, primarily with a bucket lid. Your bucket should also remain in a safe and shaded place. If you seal your bucket with a lid, make sure to puncture the lid for airflow. You might also want to incorporate a protective barrier internally, as mentioned above. 
  • Place your fish fertilizer in an area where the smell isn’t an issue. Fish fertilizer smells, especially during the fermentation process. It’s best to have it in an area where the air is flowing and fresh. If not, check the area often for the smell. 
  • Stir and turn the bucket daily, helping the fish decompose. Your fish needs to break down, and the entire mixture needs to dissolve into a fertilizer before you can use it. This requires a bit of help on your end. Mix your ingredients daily. 
  • Check your mixture for bug infestations. Sometimes, bugs can crawl into fertilizer mixture without you knowing, and this can be an issue. Additionally, the fermenting mixture can overflow in the bucket and make a mess if not careful. Watch over your mixture daily to make sure everything runs smoothly. 

7. Dilute Your Fertilizer 

You have finally achieved your own homemade fish fertilizer. After two weeks to a month of fertilization, your formula is ready to use. However, it’s best to remember that you do not want to smother your plants with fertilizer. 

All fertilizers of any kind should be diluted with water for proper exposure. For fish fertilizer, one gallon (3.8 L) of water can be mixed with two tablespoons (30 ml) of fertilizer. 

If you want a stronger fertilizer, you can mix it in an extra tablespoon (15 ml). Fertilizer is best mixed in a spray bottle and used on a monthly basis. Fertilizer should be applied to the roots of your plants. 

Fish fertilizer can also be used as a foliar fertilizer. Foliar fertilizer is designed as a fertilizer that is given to the leaves of a plant. Many make homemade fertilizer for this exact reason. 

Due to the sensitivity of many plants, one tablespoon (15 ml) of fertilizer is mixed with one gallon (3.8 L) of water. The application process for foliar fertilizer should be applied with mist during cool temperatures. 

If using this fertilizer as a soil drench, you can add ½ a cup (120 ml) of fertilizer with a gallon (3.8 L) of water to the soil.

The possibility of over-fertilization is a worry for many. If this is you, lean on the safe side of measurements. Less is always more when it comes to fertilization. 

8. Store the Excess Fertilizer in a Safe Place 

Homemade fish fertilizer is generally produced in large quantities. A 3-gallon or 5-gallon (11.3 or 19-liter) bucket can produce enough fertilizer for an entire year, especially if you do not have a huge garden or collection of plants. 

Fish fertilizer, as most know, smells. And the smell can increase over time. Fish fertilizer should be stored in an area where smell can be handled. 

It’s good to also have it in a place where airflow is plentiful. If having it stored in an outdoor space, keep an eye on it often. Bugs tend to find fish fertilizer quickly and love to infest as mentioned prior. 

Like other fertilizers, this formula should only be used during a plant’s growing season. 

Avoid Using Chemicals To Dilute the Smell 

Many choose synthetic fish fertilizers or options that are not as organic as they say they are because they do not want to deal with the hassle of storing fish fertilizer. The smell of fish fertilizer is horrendous, it can cause messes, and no one wants to deal with the storing process for an entire year. 

The ideal solution is to add a chemical or an ingredient that masks the smell. However, many chemicals that are readily sold in stores can dilute and take away the positive benefits that come with homemade fish fertilizer. 

It is recommended not to utilize any chemicals in your homemade formula. If the smell becomes a big issue, you may want to consider switching to a premade option available at garden stores or online.

Final Thoughts 

Homemade fish fertilizer has many benefits and qualities that you cannot find elsewhere. If accomplished properly, your fish fertilizer will help your plants grow and blossom in an organic and chemical-free way. 

Grab your bowl, gather your ingredients, and make something great for your plants. You will not regret it at the end of the day. 

You can read my other article on fertilizing indoor and outdoor plants here: How to Fertilize Indoor & Outdoor Plants (Ultimate Guide)

Alexander Picot

Alexander Picot is the principal creator of, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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