What is the distance between your bulbs?
Velcro adjustable, currently at about 6".
Also, did you use 1x6 stock? Why?
I think it was 1x6 for the sides, and 1x10 for the top.
I wanted the exterior to be as clean, seamless, and simple as possible, with the only exception being the finish. No exposed plywood edges, or veneers to cover them up. No visible hardware or fasteners except on the top. Rounded edges. And I have limited skills and tools. Solid wood seemed the easiest choice. It's a bit heavy, but suspended by the spring tensioners, it's almost weightless above the tank.
You can use anything you want. This isn't meant to be a woodworking tutorial, those details really only serve as an example to show that even a mostly clueless person can make something nice.