ARE MY FISH GROWING TOO BIG FOR THEIR TANK?

Use the formula for space in the first FAQ and change the tank if your fish are growing too big for it. Goldfish can double in size within a few months, and this means double the excreta. Goldfish have to swim in their own loo. The problem is not the visible solids but the invisible ammonia, the equivalent of our urine. You can buy home test kits which will test for ammonia, nitrite and pH. Alternatively, many aquarium shops offer a water testing service for a small fee. Take them some aquarium water in a clean glass jar."