We have a raised wall waterfall attached to our pool which dumps water about 3-4 ft into the pool. It uses the same filtration but has its own pump. For various reasons we almost never use it, so of course it becomes a virtual cesspool of algae, debris, dead mice & mosquitos. Even if we don't turn it on, once it rains again (like it will tonight), it all overflows into the pool. It's about 4 ft deep, so it never evaporates entirely. What do other people do? Does it need to be so deep? Can we extend a pipe for the water flow and fill most of the space with rocks? Should I be running it daily, and if so for how long (which would get pricey)? At this point I just want to cement the whole thing over and call it a day.