Cleaning your aquarium? Don't pour the water down the drain! Here's why dirty fish tank water can benefit your plants.
Use Fish Tank Water to Nourish Your Plants
Published on Nov. 20, 2024
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Don’t Waste Fish Tank Water
If you have pet fish, you know all about cleaning tanks. It’s necessary, if unglamorous, work — and it’s all part of keeping your fish healthy and happy. With that said, you might feel badly about wasting tank water. Depending on how many fish you have, it can be a lot to just dump down the drain. Is there anything useful you can do with it? Turns out, there is! You can use fish tank water for your plants. Here’s how, and why, dirty aquarium water works to benefit your garden.
Did you know you can use “banana water” for your plants, too?
Why Fish Tank Water Helps Your Plants
Tank water can be incredibly useful for your plants, with a few exceptions (which we’ll get to later). Over time, this water builds up nutrients, such as nitrogen and potassium, that plants use to grow. Because of that, watering your plants with water from your fish tank can be of immense benefit to them. It’s like free fertilizer. Who knew?
Concerned plant parents might wonder, though, if using tank water is safe — after all, adding too many nutrients can kill plants with kindness. In most cases, aquarium water should be fine for your plants. As long as you’re changing the water in your tanks regularly, the nutrient buildup shouldn’t be so high that it causes harm.
If the water has been in the tank for a very long time, you might need to dilute it a bit to prevent excess nutrients from overpowering your plants.
Got questions about plant fertilizer? Read our guide to learn how to feed your garden
When Shouldn’t You Reuse Fish Tank Water?
With that said, there are a few circumstances under which you definitely shouldn’t use your fish tank water on plants. The first, and perhaps most obvious, is when it comes to saltwater aquariums. Saltwater can be very harmful to plants, so make sure you only use water from freshwater tanks for this tip.
In addition, aquarium water shouldn’t be used on plants you intend to eat (such as your kitchen herbs or tomatoes) — especially if you’ve added chemicals to the water.
How to Use Fish Tank Water for Plants
This part is easy — just drain the tank, keep the water, and use it when you water your garden! Then refill the tank with clean water and start the cycle over again. It’s that simple.
Using tank water is easy, and it benefits both your pet fish, who get clean water, and your plants, which gain more nutrients. It’s a win-win.
Next, learn the right way to water indoor plants — and why you might be watering yours incorrectly.
Sources
- Horticulture Magazine, “Watering Houseplants With Fish Tank Water“
- Gardening Know-How, “Plants Watered With Fish Tank Water: Using Aquarium Water to Irrigate Plants“
- University of Wisconsin-Madison Division of Extension
- University of Minnesota Extension – Quick Guide to Fertilizing Plants
