Liquid agent for reducing the pH value of water.
 In addition to reducing the pH value, pH MINUS softens the water and prevents the separation of limescale on the surfaces of the pool and equipment.
 100–150 ml of pH-minus 50% per 10 m³ of water usually lowers the pH by about 0.1 unit.
 The exact amount is determined experimentally because it depends on the hardness and composition of the water.