Houseplant enthusiasts often spend money on liquid fertilisers, but there is a free alternative available. Fish tank owners regularly change water, discarding litres of nutrient-rich liquid. Instead of pouring it away, this water can be used to feed houseplants.
Why Aquarium Water Works
Water from a freshwater aquarium contains nitrogen, phosphorus, and beneficial bacteria. These nutrients can promote healthy plant growth without additional cost. The water should only come from a tank that is cleaned frequently to avoid harmful buildup.
How to Use It
Collect the water during a partial water change. Let it reach room temperature before applying it to plants, just as you would with any liquid feed. The water may have a slight odour, but it dissipates quickly.
Test Results
In a month-long test, aquarium water was used on a monstera and a peace lily. Both plants showed healthy growth, with the peace lily producing a new leaf. The water's smell faded soon after application.
Verdict
Aquarium water is a useful supplement but not a complete replacement for balanced fertiliser. Nutrient ratios vary depending on the tank, fish, and feeding schedule. However, as a between-feeds boost, it reduces waste and provides free nutrients.
