Fluval AquaClear AC20 Aquarium Backpack Filter, 379 lph

4-stage filtration (2x mechanical, chemical, biological) for superior water clarity and quality CycleGuard preserves the biological balance of your aquarium by independent media replacement, which prevents disruption of the nitrogen cycle and is essential to keeping water clean and healthy. Patented refiltration system prolongs contact time with the medium for a cleaner, healthier, and biologically stable aquarium. Inlet pre-filter keeps algae filaments and debris away from pump for consistent water flow Adjustable flow control for precise fit