I made a really simple hood for my 4 footer out of marine ply - http://www.bunnings..../plywood-sheets
It was a rush job until I have time to do it stylish, but it's been solid for a few months without condensation etc, and I took my glass off.
I got Bunnings in Belmont to cut the wood into the sections needed so I'd get a nice straight edge, they do it for free, but have an OHS prescribed minimum leftover edge policy that might mean buying an extra sheet and having more unusable offcuts.
The construction is basic. Tank is 4x2 (60x120), so here were the section sizes I needed -
top - 60 x 120
front/back - 30 x 120 (It's a bit tall, I'll probably drop to 15-20 on the next build)
left/right/centre lateral - 30 x 60 (also drop 15-20 next build).
Add some millimetres where required to account for the thickness of ply you use so you can get it sitting flush on or over the tank.
I used 12mm on all pieces except the top so there's enough wood to screw into the side of. Top was thinner to cut costs, reduce weight and because the screws only go through, not into it. Depending on your filtration system, a jigsaw is hand to accommodate the plumbing. A hole for 19mm tubing attached to a garden hose fitting makes water changes possible without having to remove the hood - http://www.bunnings....11109b_p3120628
Another thing that probably helps reduce moisture buildup is the PC case fans that are rigged up inside to keep my budget LED heatsinks cool. I'd assume LED lighting to be the best option, and any unit with a fan would be good. If you already have other lighting, the PC case fans are pretty cheap from any computer shop or Altronics, and if you want you can cut a section out of the back to rig it up as extractor fan. I think the air movement helps to increase O2/CO2 transfer on the water surface too.