At the bottom of most ponds, there will be a built up of sludge. Sludge is caused by decomposing plant, animal and fish waste matter. Over time the sludge can harbour harmful bacteria and micro-organisms that cause disease and infection and can turn your pond water cloudy and unsightly. By using Bermuda Banish Pond sludge, you can safely and effectively removes the sludge without upsetting the ponds natural balance. 500ml will treat ponds up to 11365 litres/ 2500 gallons in size.