Tetra Pond 500ml FilterStart Filter ActivatorTetra Pond FilterStart activates the pond filter after winter or when setting up a new pond and extends the intervals between cleaning. It contains a mix of highly active filter bacteria, which break down harmful substances, and sludge reducing cleaning bacteria. Effective and beneficial bacteria in the filter are important for maintaining a healthy biological balance and good water quality. The living filter bacteria reduce the pollutants (ammonium