The invention provides a liquid composition when used for maintenance of a body of water, the liquid composition comprising a solution of magnesium and potassium salts, at least one of which is a halide salt. Preferably, the liquid composition comprises Mg2+ from the magnesium salt in an amount of from about 6000 ppm to about 15 000 ppm; K+ from the potassium salt in an amount from about 40 000 ppm to about 120 000 ppm and hypohalite from the halide in an amount from about 100 000 ppm to about 400 000 ppm.