This one I made out of a piece of 6mm plywood that remained from something I made. I made it to have a temporary lighting fixture until I received my custom made hood. It turned out to be quite easy and quick. It takes about $2 of wood, $4 at most. The downside it that this one holds only two tubes, certainly not enough for most peoples' needs here if normal fluorescents used (not even mines, just provisional), maybe better for PC lighting.
You will need:
2 6mm-9mm plywood pieces about 5 inches wide, long enough to fit the rim of your tank, both same exact length.
2 1/2 inch thick, 1.5x1.5 wood squares. You could use triangles, but squares are easier to cut. For a less cheesy side look, use rectangular triangles, the sides should be the same length than the width of the long boards, in this case 5 inches.
4 1x1 thin plywood squares. These will be the bases to screw the clips to the inside of the fixture, specially if you use the 6mm plywood.
4 Clips to hold T8 bulbs
4 Screws to fix the clips, not too long, half an inch maybe (usually come with the clips)
1 Small square piece of ˝ inch thick wood, about 1x1 . Can be smaller, it is just to give the fixture some grip in the middle.
Duct or electric tape.
The ballast(s) and bulbs you will use. The 6mm plywood won't be strong enough for heavy metalic giant balasts. Compact, light plastic ballasts (some metalic are light enough, though) are recommended for this fixture.
Hammer, nails, glue, screwdriver, and someone to help you hold the thing while you nail it, specially when they are long like 3 and 4 footers.
Glue the four small squares to the boards on the side that will be the inside, a little closer to the side that will go downwards, to have the tubes more separated, but where they won’t tpuch the glass. Just check if it would fit. Place them close to the tips, about 2-4 inches. More if you want, whatever. There you will screw the clips, because screw needed to hold a tube will pierce through the 6mm plywood, 9mm perhaps would hold the screw, but this also separates the tube from the board a bit more.
Then, glue and nail the boards to the squares or triangles in the borders, making a 90° angle, and the small piece of wood in the center. Paint it white inside, and any colour you like outside. Sealer/primer are advised. Seal junction of the boards by the inside with tape, this is just to avoid light leak.
Screw the ballasts to the rear outside of he fixture, and drill a hole (or two if needed) on the board to take the wires inside. Just put the endcaps, the plug, insert the tubes, and ready. You can of course add a switch if you want.
This is supposed to rest on a glass cover to avoid damage to the wood due to water and moisture
Here are the pictures. They say little about the construction, I did not consider it worthy of a DIY post until I finished it. Some are not good, blurry, particularly the ones that needed to show detail. I hadn't painted the inside nor drilled the wiring hole when I took them. I did not make a proper plug beacuse I was to use the ballasts in another fixture lately, however, I did change their positions do all cables headed to the center.
Fixture on the bed
...on the tank
A few details of construction
These are the ballast I like so much, I put my hand next to them to show their diminute size. They can be seen too in the first pictures.