Ammonia is produced when uneaten food and waste decompose. This is highly stressful and toxic to fish if left to accumulate within the aquarium. To know if you have a build up of ammonia, test weekly.

Ammonia is produced by fish as they breathe and pass waste into aquarium water. Other sources include decomposing waste from uneaten food and other organic contributors. This is highly stressful and toxic to fish, in particular in new aquariums and if left to accumulate within the aquarium fish loss will occur. To know if you have a build up of ammonia, test weekly to ensure ammonia is detected or more frequently during new aquarium establishment, post medicating, etc.