(2 Pack) Zoo Med 511 Mechanical Filter Sponges - Coarse. Turtle Clean 511 mechanical filter sponge is the first line of defense in removing dirt and floating debris from your terrarium or aquarium. Although filters are used to keep your water clean and safe, Zoo Med also recommends weekly water changes of at least 20%. When adding tap water make sure you add Zoo Med's Reptisafe to remove chlorine and chloramines.