Fluval AquaClear 20/30 BioMax Filter Insert provides an optimal environment for the colonization and growth of beneficial bacteria, which is essential for effective biological filtration and water purification. BioMax’s complex bio-ring pore structure allows beneficial, toxin-reducing bacteria to thrive. By reducing toxins such as ammonia and nitrite, BioMax effectively increases biological filtration efficiency by 30%. Exclusively designed for the AquaClear 30 Power Filter, BioMax is suitable for fresh and saltwater aquariums. BioMax comes in a mesh bag for quick and easy installation.