Cleans algae and hard water stains Non-toxic and fragrance-free Use 1 per tank to avoid cross contamination Stop spending hours scrubbing algae off the sides of your tank and use an algae scrubber sponge instead. Add just a little bit of elbow grease, and algae, hard water stains, and dirt won't stand a chance. This sponge is small but mighty — perfect for touch-ups and touch cleaning at our store and warehouse.  You will receive 3 algae scrubbers in each pack.  Sponge measures 2.4″ x 4.6″ x 0.93″ Made from non-toxic melamine foam — completely fragrance-free with no extra chemicals or additives Can be used on glass or acrylic tanks