How to Use Aquarium Water As Plant Food


Anyone who owns fish as pets knows there's a lot of regular maintenance needed for the health of your pets. One of these tasks is changing the water, a simple process of removing up to half the water in the tank and replacing it with fresh water. In the end, you are left with a bucket of nutrient-rich waste water from the freshwater aquarium that easily can be used as plant food.

Step 1

Place your bucket next to the freshwater aquarium so the bucket is lower than the tank. Place your siphon tubing into the aquarium and let the entire tube fill with water.

Step 2

Cap the ends of the tubing with your thumbs to seal the water in. Leave one end inside the tank under the water and move the other end to hold it over the bucket.

Step 3

Release your thumbs to allow the water to run "downhill" into the bucket, starting a siphon of the tank water in the process. Dig the end of the tubing that is in the tank around in the gravel to stir up and suck away excess fish waste.

Step 4

Take up to half of the water from the tank all the while continuing to unsettle the material caught in the bottom. Bring the end in the tube up above the water level to stop the siphon when you are finished removing water or your bucket is full.

Step 5

Fill your watering can with the water from the bucket and water your houseplants and outdoor potted plants with it in place of your regular watering. While you don't want to water with this water every time, the aquarium water can be used up to every other watering without fear of harming your plants.

Step 6

Water your outdoor plants by taking the bucket to the site of your plants and slowly pouring from the bucket or using the watering can to give those plants extra food. Annual flowers and perennial foliage plants respond best.

Tips and Warnings

  • If you have neglected your tank and it has been more than two months since the last water change, don't use this water on your plants as the buildup of nitrogen and ammonia may be too high and could scald the roots of sensitive plants.

Things You'll Need

  • Freshwater aquarium
  • Five-gallon bucket
  • Plastic siphon tubing
  • Watering can


  • "Tropical Fish"; Bruce W. Halstead and Bonnie L. Landa; 1975
  • "Reader's Digest Illustrated Guide to Gardening"; Carroll C. Calkins; 1993
Keywords: aquarium water as plant food, fish waste, nitrogen plants

About this Author

Margaret Telsch-Williams is a freelance, fiction, and poetry writer from the Blue Ridge mountains. When not writing articles for Demand Studios, she works for as a contributor and podcast co-host.