Cascade Power Filter Bio-Sponge CartridgeCascade Power Filter Bio Sponge Cartridges are convenient replacements to keep your Cascade filter running at peak efficiency. These duraple bio sponges optimize colonization of beneficial aerobic bacteria, allowing the filter to remove ammonia and nitrites from your aquarium. Optimizes colonization of benedicial aerobic bacteria Removes ammonia and nitrites keepting the aquarium healthy Convenient, no fuss replacement sponge Easy to replace: just