Aqueon Ammonia Reducer for QuietFlow LED Pro Power Filter 20/75 are designed to address common water issues. The pads are pre-cut to fit in the Aqueon QuietFlow LED PRO Power Filter Bio-Media Grid. Ammonia Reducing Pads help to remove excess harmful or toxic ammonia Pre-cut for easy installation Fits in QuietFlow PRO Power Filter 20/75 For optimal performance, replace approximately every 2 to 3 weeks