Tetra Pond Sludge Reducer Naturally Minimizes Sludge In Ponds, And Improves Water Clarity. Safe for use in ponds with fish & plants. Adding beneficial bacteria to pond water produces enzymes that degrade organic debris to naturally reduce sludgy build-up. Helps remove the sludge on the bottom of ponds to make the water clearer. 40 Oz. treats up to 40,000 Gallons.