Best Practice Guide to Eco-Safe Water Changes
For hobbyists, disposal of water from our regular water changes requires some care to help
prevent spread of aquatic diseases in New Zealand waterways.
In an ideal world, it is best not to dispose of untreated waste water down the drain as it goes
directly into our waterways. Ideally, you should always treat waste water with a disinfectant
like chlorine bleach (Janola) to kill bacteria and viruses. As chlorine is highly toxic to fishes,
chlorine should never be added directly to the aquarium unless the tank is completely empty
To disinfect waste water, remove water into a holding barrel and add 5mls of bleach per litre
of water (or 1-5mg/L). Let the water sit in the barrel for about an hour. After the hour has
passed, the water is then then safe to dispose of down the drain. If you wish to use the water
on your lawn or ornamental garden instead, you can add a dechlorinator like Seachem
Prime after the hour has passed, then just pour the water out onto the lawn as needed.
If you are not able to dechlorinate your tank water, try to avoid disposing of water down the
drain as this will risk spreading aquatic disease in our waterways. Instead, freshwater can
safely be added to your ornamental garden or lawn (but avoid adding it to your vegetable
garden or disposing of it near drains or waterways).