Special order item. Please allow for extra time.Phosphate free. For those sensitive situations such as planted tanks running CO2. General KH Alkaline Buffer slowly raises KH (carbonate hardness) by approximately 1dKH or 18ppm at a time. Being an alkaline buffer, it has a high pH and this counteracts the acidity from the CO2, stabilising pH and reducing stress on fish. Suitable for both fresh and salt water aquariums. Directions: 1 level teaspoon or 5g to 60 litres of water will raise KH by approximately 1dKH or 18ppm and will raise and stabilise pH. For planted tanks using CO2 systems, use cautiously with small doses to avoid large pH increases.