The AquaClear CycleGuard Power Filter is a versatile clip-on filter that uses a multi-stage filtration system to improve water quality. The CycleGuard system provides three types of filtration: mechanical， chemical and biological. In this unique system， only one component is changed at a time to protect the beneficial bacteria that’s usually thrown out with cartridge filtration systems. The AquaClear CycleGuard Power Filter comes with AquaClear Foam， Activated Carbon and BioMax filter inserts. As the water filters through， these inserts help preserve good bacteria， trap debris and remove impurities for a stress-free environment. The patented refiltration feature lets you control the flow rate for more delicate fish and plants.