Rather than pouring away old aquarium water, you could use it as free plant feed.
The problem
Houseplants need liquid fertiliser, but this can be expensive. Fish tank owners, meanwhile, produce litres of nutrient-rich water during water changes, which then gets poured away. Could it feed houseplants instead?
The hack
Water from a freshwater aquarium contains nitrogen, phosphorus and beneficial bacteria. Rather than discarding it during routine water changes, use it to water your houseplants, giving them a free feed.
The method
Only use water from a freshwater tank that is changed often. Collect the water during a partial water change. Allow it to reach room temperature before using it on your plants, then apply as you would any water with liquid feed.
The test
I used aquarium water on a monstera and a peace lily for a month. Both plants showed healthy growth, and the peace lily pushed out a new leaf. The water did have an odour, but it faded quickly.
The verdict
Aquarium water is a useful resource. It will not entirely replace a balanced fertiliser, as the nutrient ratios will vary depending on the tank, the fish and how recently they were fed. But as a supplement between proper feeds, it is considerably less wasteful than watching it disappear down the plughole.
