Fish Tank & Pond Sponge Filter Foam - Various Sizes. Transform Your Aquarium into a Thriving Aquatic Haven with This High-efficiency Biochemical Filter. Suitable for Both Freshwater and Marine Environments, This Advanced Filter Boasts a Multi-porous Structure That Effectively Breaks Down Waste and Leftover Food. By Minimizing Blockages and Maximizing the Surface Area for Beneficial Bacterial Growth, It Ensures Crystal-clear Water and Promotes Optimal Aquatic Health. Constructed from Durable, Lightweight Materials, This Filter Guarantees Excellent Water Flow and Efficiently Captures Debris. Its Eco-friendly Design Allows for Easy Cleaning and Reusability, Making It Perfect for Aquariums of All Sizes. Features: - Compatible with Freshwater and Marine Environments - Adaptable to Various Tank Sizes - Lightweight for Optimal Water Flow - Promotes Biological Filtration with Nitrifying Bacteria - Easy to Clean and Reusable - Multiple Pore Sizes: S (50ppi), M (35ppi), L (25ppi), XL (15ppi) - Available Sizes: 50x12x2cm to 50x50x5cm - Recommended Replacement Every Three Months Package Includes: - 1 X Biochemical Filter Cotton (black).