Placed in flowing water such as on the steps of a waterfall or in the bubbles of an aerator or fountain, Pond Zingers slowly dissolve, releasing components into the water that act like magnets to bind excess inanimate nutrients together. Pond Zingers are designed to clean ponds from 500 to 12,000 gallons. They are absolutely safe for fish and will not alter the pH of your water. In addition to receiving numerous excellence awards, Applied Polymer Systems\' products have been tested or used by universities, water management districts, and Department of Transportation agencies who have proven them to work well and be safe for the environment. Safe for Fish For ponds from 500-12,000 gallons An environmentally friendly way to turn dirty ponds clean Easy to Install