As you can see in first pictures, I have a 5 gallon sump underneath. I'm going to plumb a PVC overflow in the tank. This way the water lever in the exo-terra will always be the same and won't get to low. It also prevents the tank from draining if there is a power outage or the pump fails.
As you can see the shelf is too high and there is almost no room to do the plumbing to the tank. I didn't plan on a 5 gallon being so tall when I built the stand. So it was a lot of work lowering the shelf since the 2x2" supports were nailed/screwed in with 3" screws.
Here is the sump now lowered ~5" so I can fit my arms in to work on the plumbing.
I am going to have a canister filter (not sure which one yet, looking for a good deal) below the tank, so I couldn't lower it much more.