I have a big metal waterer hanging about 8 inches above the floor. In a day or 2 I have to empty, WASH and refill it. Scunge gets into the trough of it, and I guess anaerobes are reproducing in the reservoir making it stink like sulfur. When I wash it, there's a slime over the inside. I would really like not to have to wash the thing almost daily. What can I do to have the water clean for longer than 24-48 hours??