The Dual Action Foam Filters are biological filters composed of open-celled foam which provides enormous amounts of usable surface area for beneficial bacteria to colonize, This bacteria breaks down harmful waste substances (ammonia and nitrite), making your aquarium a safer environment for your fish to live and breed, This fundamental filter is excellent for breeding all types of aquarium fish, as well as for hatching and raising brine shrimp as it will not trap nor harm them, The Dual Action Foam Filters are available in 4 models to accommodate the filtering needs of various-sized aquariums, SKU: RYLHC2925