This Fish Tank Biochemical Filter Sponge is suitable for use in saltwater tanks, freshwater tanks, and planted aquariums. The sponge can be easily cut to fit your desired size. Made of durable cotton material, this thickened filter sponge is strong and long-lasting. It provides good light diffusion, helping to reduce algae growth. The evenly sized pores promote the cultivation of high-density nitrifying bacteria for improved biological filtration. Features: - Color: Black - Material: Cotton - Size: 50x50x4 cm - Suitable for saltwater, freshwater, and planted aquariums - Can be trimmed to fit - Thickened design for durability - Helps reduce algae growth through shading - Optimized pore size supports beneficial bacteria colonization Note: Due to lighting effects, monitor brightness, and manual measurement, slight variations in color and size may occur between the product image and the actual item.