A healthy, balanced aquarium relies on beneficial bacteria to break down fish waste, dead plant material and other organic debris that accumulate in the tank. They keep the water crystal clear and prevent toxic ammonia and nitrite from accumulating. These bacteria live in the filter media and on solid surfaces in the aquarium, such as gravel, rocks, plants and decorations, but it takes time to get them established.
Why Are Beneficial Bacteria Important?
Newly set up aquariums sometimes experience dangerous spikes in ammonia and nitrite from fish waste due to a lack of these bacteria. This happens when more fish or food are added than the existing bacteria can process. Ammonia is released by fish as waste and is broken down by beneficial “nitrifying” bacteria to nitrite and then nitrate, in what is known as the Nitrogen Cycle. Both ammonia and nitrite are highly toxic to fish. It’s important to add fish gradually to new aquariums and feed sparingly at first to give beneficial bacteria time to colonize the tank and filter.
In established aquariums, accumulation of solid fish waste, uneaten food, dead plant material and other organic debris can cause a deterioration in water quality and a drop in pH. This is especially true in tanks containing goldfish, large cichlids, piranhas and other predatory fish.