Yea your water level is way too high. You will not get proper filtration with this.
I have a reef casa flat 12 gallon. My water level sits about 1/2-3/4 at the surface teeth. Are you using the standard pump that came with it?
I'd pull a cup of water out of the main display tank and watch as the chambers level out. The first chamber to lose water is your return pump chamber. If its water level does not drop. Continue to pull a cup of water out, wait a few minutes then check its level again. Do this until your main display tank water level is about 3/4 on the surface teeth and your return pump chamber water level is just below the middle chamber by an inch or 2 is fine. If you pull water out and see your return pump chamber rapidly lose water. Then your return pump is too much and you need to slow it down. The reef casa pump should have an adjustable speed.