I recently purchased an AquaC EV-180 skimmer. This is my first time using an in-sump skimmer. The directions show that the gate value should be above the water line. Can someone please tell me if it has to be totally above the water or if part of it can be under water? I donÃ¢â‚¬â„¢t have a lot of room under the stand to raise it.