Maintain a healthy， clean aquarium by growing beneficial bacteria with the AquaClear BioMax Filter Insert. One of the most effective ways to maintain good water quality and keep your fish thriving is by seeding your aquarium with good bacteria. This bacteria breaks down harmful ammonia and nitrite from fish waste and other organic matter and starts the essential nitrogen cycle in your aquarium. Prepackaged in a mesh bag for easy installation， BioMax’s complex bio-ring pore structure allows beneficial， toxin-reducing bacteria to thrive， which in turn increases biological filtration efficiency by up to 30%. Exclusively designed to fit the AquaClear Mini CycleGuard Power Filter， Size 20， this BioMax filter insert is suitable for fresh and saltwater aquariums.