The use of copper and silver ions for purifying water has been practised for centuries. The ancient Greeks found that water kept in silver containers was mysteriously purified and that algae didn't grow in copper water pots. The modern metal systems using silver and copper (nature's bacteriacide and algaecide) are effective and now popular with their very easy care and minimal maintenance. Silver kills over 640 pathogens and viruses while copper kills all algae including black spot. This combined with an oxidiser which removes organic waste that has entered the pool from people using it (body fluids, sweat, sunscreen and the like) ensures a safe and healthy chlorine-free swimming experience. No need to shower or wash bathers and towels after every swim. That alone is less hassle and the best part is that the water can also be recycled to water the garden or grass. Another eco-friendly alternative!