sump/wet/dry question

[glubglub]

I'm using a ProClear Aquatics Premier 125 Gallon Wet Dry Filter with a
CA 2200 pump as a return to my 75 gal tank. The problem is the sump starts blowing air bubbles into the main in a couple days. seems the main tank is maxed on water level and the sump is low sucking air to the main.
any help woul;d be appreciated.
thanks
glub

 

[jdl]

sump is low from evaporation?
if so, add some water
sump is low because your return pump sends more water then your drain?
if so, you can put a ball valve on the pump and send less water into the display.

 

[glubglub]

I'm thinking it's a combo of both evaporation and the pump doing too good of job. I find myself topping the sump off every couple days with a gal or so. this may be normall giving the size of my sump (approx 12 gal). thanks for the baLL valve idea. I'll try it and post the result.