Aquarium Water for Watering Plants

Many aquarium hobbyists pour hundreds or even thousands of gallons of aquarium water down the drain every year. Most don't realize that in addition to wasting water, they're wasting large quantities of natural fertilizer that is highly beneficial to most plants. Plants treated with aquarium water will thrive on the fish waste and other organic compounds that it contains.

  1. Waste Breakdown

    • Over time, natural compounds build up in aquariums from the breakdown of waste produced by fish. In established aquariums (typically those that have had fish for six weeks or longer), bacteria are at work, feeding on the byproducts of fish waste. In this process, ammonia is converted to nitrites, and nitrites are converted to nitrates. Phosphates are also produced in smaller quantities.

    The Facts

    • In high concentrations, nitrates and phosphates can be harmful to fish. To keep the levels of nitrates and phosphates safe for their fish, aquarium owners change the water in their aquariums frequently, replacing a certain percentage of water with fresh tap water. In many cases, hobbyists pour the water they've removed from their fish tanks down the sink or toilet.

    Considerations

    • If you changed 10 gallons of water every week, that amounts to over 500 gallons per year. People with larger aquariums or multiple tanks will likely change over 50 gallons per week, amounting to over 2,500 gallons per year. That's a lot of water to pour down your drain! Many hobbyists don't realize that the compounds in the water they're removing are found in most fertilizers. Nitrogen is not only the most common element found in commercial fertilizers, it's also the most common element found in aquarium water, primarily in nitrates.

    Applications

    • You don't need to do anything special with your aquarium water to use it for plants. It can simply be collected in containers and poured directly on houseplants, outside flowers, shrubs and even lawns. If you don't have any plants that need to be watered, consider offering your aquarium water to a neighbor who does. It will lower their water bill and help their plants grow.

    Warnings

    • Aquarium water is beneficial to almost all plants. However, use caution if your aquarium water contains chemical additives like algae destroyers, which are very harmful to plants. Medications typically contain chemicals that are not healthy for your plants, either. Salt that you might have added to your aquarium may also be harmful to your plants.

    Environmental Benefits

    • If you don't add chemicals to your aquarium, there's no better way to use your aquarium water than by watering your plants. By doing so, you're conserving water and helping your plants grow. It's a benefit to you, your plants and the environment.