AquaClear Bio-Max Inserts increase the biological filtration efficiency of your aquarium filter, while enhancing its ability to reduce harmful ammonia and nitrites. These highly porous ceramic rings provide maximum surface area to facilitate the growth of beneficial bacteria. These bacteria break down toxic water contaminants and help to create a clean, healthy aquatic habitat for your aquarium fish.Expands biological capacity of aquariumsProvides optimal living conditions for beneficial bacteriaEnhances ammonia and nitrite reductionSafe for fresh and saltwater useSizing: Sized to fit AquaClear Aquarium Filters.Size 20: 5-20 gallon aquariumsSize 30: 10-30 gallon aquariumsSize 50: 20-50 gallon aquariumsSize 70: 40-70 gallon aquariumsSize 110: 60-110 gallon aquariums