Fluval Peat Granules are the all-natural way to soften aquarium water and achieve the pH levels required for breeding and rearing certain tropical fish. Peat contains humic acid, tanning agents, and trace elements that are essential for various life processes. Highly concentrated for maximum effectiveness, this product is recommended for fish that prefer soft, acidic water. To ensure optimal conditions, it's best to test with Nutrafin pH and KH test kits on a regular basis to verify that desired levels are being maintained. A KH range of 50-120 mg/L (approximately 3-7 dKH) is usually recommended for fish that thrive in soft, acidic water. Use Nutrafin pH Stabilizer for superior results in maintaining an optimal KH value. For filter models: 106, 206, 306, 406, FX5, 105, 205, 305, 405, 104, 204, 304, 404.