The outside of the power cartridge features polyester foam to trap fine particles; while the inside chambers contain carbon to remove pollutants and odors; and zeolite to eliminate toxic ammonia for a cleaner, healthier aquarium environment and crystal clear water.The Bio-Screen, with its large surface area, is designed to promote the growth of friendly bacteria.Enhances aquarium water quality.Bottom positioned motor for quiet operation.Waterfall spout for continuous oxygenation.Effective 3 stage Filtration (mechanical, chemical, biological).Bio Screen provides large surface area for growth of friendly bacteria.Easy replacement of Power Cartridge.Compact size and energy efficient.Refill Power Cartridges available (A308, sold separately).