Tetra FilterActive contains a mix of living starter and sludge-reducing cleaning bacteria. Some important bacteria are lost through the regular cleaning an aquarium requires. Tetra FilterActive rebalances bacteria lost when the water is changed or the filter is cleaned. Tetra FilterActive contains living starter bacteria that settle in the filter on the filter material and maintain the biological balance in the aquarium. These nitrifiers are important for breaking down nitrite and ammonia, which are harmful to fish. This product provides immediate support for the biological activity in the aquarium. Tetra FilterActive also contains sludge-reducing cleaning bacteria that keep the filter cleaner for longer with their natural action. They accelerate the biological decomposition of organic pollutants such as fish waste, built-up sludge, food remains and dead plant materials. This improves the filter’s performance and extends the intervals between cleaning. It also promotes bioactivity in the substrate and prevents decay. This helps to keep the aquarium inhabitants happy and healthy and reduces the maintenance the aquarium needs. Tetra FilterActive contains natural bacterial cultures and is 100% biological. Its liquid formula is very easy to use and does not cloud the water. It can also be used to support the biological activity in the aquarium when new fish are added or the water is heavily contaminated due to a large number of fish.