Zoo Med (3 Pack) 511 Mechanical Filter SpongeZoo Med's 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 percent. When adding tap water (during a water change), make sure you add Zoo Med's ReptiSafe to remove chlorine and chloramines.