Penn Plax Pro-Z Ammonia-Removing Zeolite Crystals for Aquarium Medium

(44oz) Pro-Z Laboratory-Quality Ammonia-Removing Zeolite crystals are fast acting, long lasting, and proven to remove ammonia, the #1 fish killer.Zeolite crystals are designed to keep your fresh water aquarium clear for up to 4-6 weeks.Recommended for use in Cascade, and all other hang-on, internal and canister filter systems.