Houseplant enthusiasts often spend money on liquid fertilisers, which can be costly. Meanwhile, fish tank owners generate litres of nutrient-rich water during routine water changes, only to discard it. Could this water serve as a free plant feed instead?
The Hack
Water from a freshwater aquarium contains nitrogen, phosphorus, and beneficial bacteria. Rather than pouring it away, you can use it to water your houseplants, providing them with a free source of nutrients.
The Method
Only use water from a freshwater tank that is cleaned regularly. Collect the water during a partial water change. Allow it to reach room temperature before applying it to your plants. Use it just as you would any water with liquid fertiliser.
The Test
I used aquarium water on a monstera and a peace lily for one month. Both plants exhibited healthy growth, and the peace lily even produced a new leaf. The water had a slight odour, but it dissipated quickly.
The Verdict
Aquarium water is a valuable resource for houseplants. However, it should not entirely replace a balanced fertiliser, as nutrient ratios vary depending on the tank, fish species, and feeding schedule. As a supplement between regular feedings, it is far less wasteful than letting it go down the drain.
