Sera kH-Test 15 ml, 0.5 fl.oz. Aquarium Test Kits In the case of too low KH values we recommend Sera KH/pH-plus (in freshwater) or sera pond bio balance (in ponds) In the case of too high values we recommend filtering through Sera super peat (in freshwater aquariums) Makes it easy to monitor the carbonate hardness in fresh and salt water 15 Milliliter / 0.5 Ounce Test Kit