The POLY-FILTER is for filtering and purifying both fresh and salt water aquariums. It is a formulation of a special patented material bonded to a synthetic matrix. By means of a unique proprietary process, the POLY-FILTER is made impervious to salt and is also organic loving to certain materials. It can absorb and adsorb contaminants and other toxic materials found in nature or added to fresh and salt water with or without fish and invertebrates. Medication added to fresh and salt water aquariums for treatment of diseased fish will automatically be removed by the POLY-FILTER after serving their intended purpose before the medication can produce a toxic effect on the fish.The POLY-FILTER is non-toxic and harmless to biological filtration because it allows a sufficient amount of ammonia to reach the biological filter in order to sustain the bacteria culture. The POLY-FILTER provides a supplemental means for removal of ammonia when the biological filter is unable to break down the excess ammonia and its concentration increases rapidly. Then the POLY-FILTER adsorbs the excess ammonia while the biological filter readjusts to higher ammonia input levels. Changes color when exhausted. 4" x 8".Poly-FilterOperating InstructionsFreshwater Application:Add Poly-Filter to any holder or apparatus at any time.Establishing Marine/Reef system:Add Poly-Filter so water can pass through it.For Maximum Filtration: Eliminate all water bypass.Poly-Filter in established marine freshwater systems: Conventional power filter: Place Poly-Filter on bottom plate. Cover with gravel or floss. Do not restrict flow. Plastic undergravel filters: Place Poly-Filter on top of the undergravel plate. Cover filter and plate with gravel. Canister-type power filters: Place Poly-Filter in the chemical filter compartment. Add floss according to manufacturer's instructions.Medication removal (parasite and antibiotic treatments):Remove Poly-Filter from water before any type of medication is added.