[Canadian]

The flat piece shown hovering above the tank is just a sort of exploded view of the "cap" as I've been referring to it. That piece is going to sit on top of the first overflow baffle and then on little struts that will be siliconed at fairly wide intervals across the most expansive part of the far right hand chamber so that the cap sits flush with the top of the glass. I will have to cut out a few notches for power cords and the mounting bracket for the Coralife clip-on light. However, if I end up adding the ATO I'll end up having to elevate this cap a bit (essentially making an inverted / open bottomed box) to allow the return tubing to come in to the chamber from behind rather than up and in (again, so it's not seen).

Here's a pic of what I was trying to explain above regarding my initial intention (although now it seems I may very well have to elevate this cap to accomodate the ATO as I suggested above)