Foam Filter InsertTraps particles and debris. Tailored fit prevents bypass. Enhances biological filtration. Safe for fresh and saltwater use. AquaClear Foam Filter Inserts perform mechanical filtration by trapping particles and debris as they pass through the insert. This unique foam, designed for use with AquaClear Power Filters, features optimal pore size for efficient mechanical and biological filtration. The AquaClear CycleGuard System Preserves Beneficial Bacteria for a Stress Free EnvironmentProvides Optimal Mechanical, Chemical, and Biological FiltrationCycleGuard ensures that there is never a depletion of beneficial bacteria. Other filtration systems require you to replace the entire insert. The AquaClear system is different. Only one of the three inserts is changed at a time. This ensures that significant amounts of beneficial bacteria always remain, resulting in a stress free environment. Activated Carbon and Ammonia Remover Inserts are sold separately. Formerly AquaClear 150.