Fluval Aquarium Filter Foam Blocks provides mechanical straining of particulate waste, It prevents particulate waste from prematurely clogging other filter media in the module stack, Although the primary purpose of Fluval Foam is mechanical filtration, biological activity will eventually occur within its pore structure, Fluval Aquarium Filter Foam Blocks Features and Benefits:, - For fresh or marine water, - Enhances biological filtration, - Prevents premature clogging, - Provides mechanical filteration of fine particles, 13"" length x 3, 3"" width x 2"" height* SKU: RCHG0515