Cascade 100 Bio-sponge 1pk Replacement. Ensure a crystal-clear, healthy aquarium with the Cascade® 100 Bio-Sponge 1-Pack Replacement. This essential aquarium filter sponge is specifically designed for the Cascade 100 Power Filter, providing superior biological filtration to maintain a thriving aquatic environment. It effectively traps debris and provides a large surface area for the growth of beneficial bacteria, which are vital for breaking down harmful waste. This easy-to-replace filter media helps keep your fish tank clean and your fish healthy with minimal effort.