Question on Circulation between two tanks

[rossb]

The hole is drilled on the inlet. I have a U tube that hooks over the side of the tank. The hole causes a bit of air to be introduced into the aquarium...which is a good thing. If the pump stops it does not syphon the tank down to the bottom of the U shaped inlet tube...which is about 3" (and below the level of the other syphon tubes). The hole is about 3/32"