How to Make Fish Fertilizer Out of Fish Scraps

Fish heads are full of nutrients that make a rich fish fertilizer.

You can make a powerful fish emulsion fertilizer at home using fish parts and scraps. Homemade fish fertilizer often works better than store-bought varieties because it is often made from higher quality fish scraps that contain more bone meal and oils. Adding a few other natural ingredients to the fertilizer mix enhances bacterial activity to make the fish emulsion even more effective. Save fish heads, tails and bone scraps to make an inexpensive organic fertilizer that works.

Things You'll Need

• Food processor
• 5-gallon plastic bucket with lid
• Newspaper, sawdust or leaves
• 12 oz. jar molasses
• 2 tbsp. Epsom salt (optional)
• 1 gallon water
• Watering can

Instructions

1. Drop fish scraps into a food processor and pulse the blade to chop the parts into a fishy mush. Add the chopped fish scraps to a 5-gallon plastic bucket until it is approximately half full. The fish will decompose into fertilizer faster when more surface area is exposed.

2. Fill the bucket to within an inch of the rim with small scraps of newspaper, dry brown leaves or sawdust. This dry material will aerate the decomposing fish and absorb released nitrogen to speed the decay process.

3. Pour the entire jar of molasses into the bucket before sealing the lid securely. A small amount of Epsom salt adds the magnesium and sulfur that are common additives in commercial fish fertilizers. The sugars in the molasses will generate more aerobic bacteria activity and keep down the smell of the rotting fish.

4. Shake the sealed bucket in every direction as briskly as possible to mix the contents thoroughly. Do this once a day to keep the bacteria working throughout the decaying matter.

5. Store the sealed bucket in a warm place that is out of direct sunlight for two weeks with daily openings and agitation. Burping and shaking the bucket daily releases gas buildup and remixes the decaying material.

6. Dilute 1 qt. of the two-week-old fish emulsion with 1 gallon of water before applying the fertilizer to plants. Using the fish fertilizer at full strength will kill or damage young plants.

7. Continue to contribute an equal amount of fish scraps and dry brown matter like leaves and sawdust as the emulsion is used. Introducing the new material to the old will jumpstart the fermentation process and give you a nearly endless supply of concentrated fertilizer.

Tips & Warnings

• Apply the fertilizer away from living areas or before a rain to avoid the strong odors.

References

• Garden Web: How Do You Make Homemade Fish/Seaweed Emulsion?
• Shenandoah Rose Society: Making Your Own Fish Emulsion

Resources

• Read this Article in Spanish