The water would have to be within 3-4" of the top of the tank. Since most folks keep their tanks full, it's usually not a problem. However, if you wanted to run the water level lower, it would just be a matter of using a longer hose from the pump to the skimmer. The model with the drain fitting is designed to be used with a waste container. The drain is in the collection cup and will keep the cup from overflowing. IMO
, this isn't a good idea because the skimmer should be cleaned long before the cup fills up.