Premium class liquid filter medium Breaks down food remainders, ammonium and nitrite biologically Provides settling area for useful purification bacteria Creates a biologically active living environment The dangerous toxic substances ammonium and nitrite are being formed permanently in aquarium water. sera bio nitrivec, a sera biotechnology product, contains millions of purification bacteria, by whose support a stable biological equilibrium forms quickly and reliably so the occurring toxic substances are broken down continuously. The additionally included mineral volcanic rock removes pollutants, effectively binds cloudiness and provided suitable settling area for the purification bacteria. For healthy, clear and biologically active water. Allows adding fish already after 24 hours when combined with sera aquatan!