Well i don't think you can change it now since it looks drilled right? But if i were you, i would have drilled it a few inches higher. My return line is drilled maybe 3 inches from the lip of the tank, with the loc-line stretching towards the surface of the water. I have minimal drainback with that setup and when my return shuts off i probably get about half a gallon of water draining back, which is nothing since there's about 3G of space in my 10G Fuge.