TMC V2 Ammonia (NH3) Reduction Filter Pad for Powerbox 200 absorbs and reduces ammonia to enhance and improve aquarium water quality. For best results:-Always ensure good water flow through the filter pad.Replace every 4 weeks, or before, if elevated levels of ammonia are detected in the water. Must be used in conjunction with regular testing of water parameters.Please note: Multiple PowerPads can be used together to enhance performance.