From what I see, your "level limiting" area is where your return pump is....and since that area is so small evaporation will take that below the pump pretty quick
Project Reef said he kill me if my aquascaping looked like my last one
Only enough water that is being pumped out will be drained.
First, you need to make sure the return opening from the overflow in your sump is 1/2 in and 1/2 out of the water using an elbow
Second, try closing part of the hole you drilled in the standpipe to different sizes to dial in the correct size. I had the same problem on both my tanks when I set them up and doing those 2 things resolved the problem!
Ewan said:Awesome cubes guys.
Chin Monster, how many streams are in there? I counted 6... Which streams do you have?
Again, very nice.
E.
I'm confused, Is your tank blocking your hallway or is it in a closet?