I have drilled the side of my tank and put an elbow up to the surface. the hole is drilled 3" (to center) down from the top of the tank on the side pane of glass. I just purchased a new pump which is now pushing about 400 gph. I have had to lower the height of the riser on the elbow to allow more water to flow in. With the lowering of the riser i now have a large gap between the water level and the overflow... I am worried my smaller fish might get in there and go down to the sump. How can i fix this? Possibly make an acrylic box that fits around the drilled hole like an overflow? Could someone please draw me some plans. I'm losing my mind after reading that Tom C thread.