Tetra Pond FilterStart biologically activates the filter in the water fountain after winter or when installing a new fountain and extends the time between cleanings and water changes. It contains a blend of carefully selected strains of highly active nitrifying bacteria that break down pollutants and reduce confusion. It includes highly active nitrifying bacteria that purify the water. It reduces the amount of pollutants (ammonia and nitrites) in the water source thanks to live cultures of nitrifying bacteria. It breaks down organic matter (fish waste, leaves, etc.) with special cleaning bacteria. It extends the lifespan of water eye filters and the time between eye cleanings. It improves water quality and prevents decay. Only biological - natural.