Making fish tea at home with leftover fish parts is stinkin’ fun!
Why might fish be good for the garden?
Homemade fish tea is a wonderful nitrogen source. Phosphorus and potassium are quite water soluble too. This is one material that provides nutrients right away and over longer periods of time. In addition to a pleasing N-P-K value, fish adds micronutrients, organic matter, beneficial bacteria, amino acids and proteins to your soil.
When you make fish tea yourself with parts leftover from meals, it will be closer to organic than many commercial fertilizers and soil amendments. Most commercial brands of fish emulsion use fish humans don’t eat. Heavy metals are prominent in “trash” fish and if you look closely at the labels at the store, they will warn you not to use them on edible or organic gardens. Additives, preservatives and stuff to calm the stench complicate the ingredients list. Surprisingly enough, sometimes these emulsions are beefed up with additional nutrients because they lack the natural fish oils or bone matter.
Read more in this book about Suspicious Ingredients in Fish Emulsion and Commercial Compost.
Where do I find fish to use for the garden?
Use trimmings and leftovers from your meals. Any part of the fish works great, including bones and skin. You may even have expired cans of sardines or tuna in the cupboard – don’t throw them away, convert them into valuable plant food.
If your pet fish have swum their last circle around the tank, don’t flush them down the toilet. Bury them near your plants or create a fish tea.
Which plants may benefit from fish?
Plants that need nitrogen are first on the list and almost any other plant in your garden is a good candidate for fish tea. Timing would be important because of the nitrogen. Nitrogen works great in the beginning for flowering and fruiting plants but not when plants start to blossom.
I like to use fish on new tomato seedlings, peppers, garlic, eggplant, cucumbers, pumpkins, lettuce, kale, cabbage, kohlrabi, peas, beans, potatoes, strawberries, blueberries, blackberries and herbs, especially those in containers.
I fertilize asparagus with fish when it is at the fern stage.
Combine fish with…
Seaweed and kelp make a nice pairing with fish because it adds additional phosphorus and potassium plus micronutrients, growth enhancers and trace minerals. Fish already contains nitrogen, so I would use materials that offer other benefits.
Homemade Fish Tea Recipe
I’ll start by saying that this recipe does not involve fermenting the fish to make an emulsion. I live too close to neighbors to do that plus I’m not fond of fermenting as you might have read in the Compost section. I also don’t like to store homemade gunk in a bottle, if I can help it. I make the solution as needed.
If I have fresh fish scraps on hand at the same time I want to fertilize, I simply let them soak in a bucket or bowl of water for a few hours, then water my plants with the liquid (after watering with plain water first).
Another trick that works well is simply using the remnants from packaged fish. After removing tuna from a can, I fill the can with water and dump the contents on my soil near plants that need nitrogen. If you fear a visitfrom wild animals or rodents, open up your compost pile and dump the fish water in the middle, then cover. The goal is free fertilizer but if you are feeling loaded and walking the aisles of a “dollar” store, you can pick up packets of fish for a buck!
When I’m cooking fish for dinner I also cook the scraps in the oven. Those will be made into fertilizer. I make sure to cut up the scraps into small pieces so that they dry completely. This works great if I’m already baking fish. When I take out the fish for dinner, I set the timer for another hour and leave the scraps in until the oven has cooled off.
Just remember to take the fish out. I’ve gotten busy and forgotten about the fish scraps a couple of times and sniffed them out a few days later as I preheated the oven to bake something.
You can also dry the fish outside during the day in full sun if you are in a location where wild animals and vermin won’t come a callin’.
Storing Dried Fish
Once the fish is completely dry and cooled off, I place it in a paper bag with a coffee filter (absorbs any leftover moisture) and store it inside am air tight plastic bag or container in the refrigerator until ready to use. I like to use fish scraps right away.
Make the Fish Tea
When I’m 1-2 days from fertilizing I place my fish scraps in bucket and add water. If you want to keep the fish from floating around, contain them in an old sock or pantyhose. Usually, I do not bag them up. For every cup of fish I add about a gallon of water.
Let the fish sit (loosely covered) for no more than a 1-2 days. Stir it every day to introduce oxygen into the solution. The compost pail in the picture below works great because the top has air holes.
If you are concerned with chlorine in city water, let the water sit uncovered for a few hours before adding the fish.
Apply the Fish Tea
Once you’re ready to fertilize, water your plants first with water only. If your fish tea is a dark color, dilute it until it looks like a weak tea. Otherwise, use the tea as-is. Water around the root zone of your plants. Use 1-3 cups per plant depending on how large the plant is. Reuse the fish for another batch if you wish.
Once you’re done using the fish tea, add any leftover scraps to the compost or bury deeply in a planting hole.
Fish Tea Foliar Spray Recipe
Add your strained and weak fish tea to a spray bottle. Early in the day or in the evening, spray the tops and undersides of leaves at least once during the growth cycle or if you think the plant needs it a few more time up until about a month before edible parts or fruits start to develop. Wait a couple weeks between applications.
To avoid leaf burn, do not spray in the middle of the day when the sun is beating directly on the leaves. Moisture on the leaves at that point will dry quickly and cause damage to the leaves. Do not spray right before a rain for obvious reasons but spraying after a rain may help nutrients soak in.
Fish Tank Tea Recipe
Some hydroponic enthusiasts grow plants directly in fish ponds. If you have a fresh water aquarium, next time you change the water, don’t dump it down the drain or outside haphazardly. Use it on plants that could benefit from the mineral nutrients and organic matter. Worried about the ammonia in the water? Most of the ammonia in fish waste will be converted by bacteria to various forms of nitrate.
Once the soil is moist from a regular watering, simply water your plants as usual with the fish tank water, making sure to not leave it sitting around unused for more than a day or two. I prefer to use fish tank water as a soil drench rather than a foliar spray.
Fish Quick Tips
- Most fish recipes will stink a little bit and so I don’t recommend using fish on houseplants. The smell does dissipate after an hour or two if you would still like to try it.
- Storing a fermented fish emulsion doesn’t appeal to me because there’s a lot more going on from a microorganism and bacteria standpoint than in chemical fertilizers. I’ve heard several accounts of volatile fish emulsions bursting in closed containers.
- If you decide to buy fish emulsion, look carefully at the package. Some labels will state that the product is NOT intended for organic crop production. Surprising? Not as much when you discover that many brands of fish emulsion have high levels of heavy metals. Read more about commercial fish emulsion in the Extras section.