Here's one I built for a 75g. Waaaaay overbuilt. I wouldn't do that again way too stinkin heavy.
After the framing I used plywood on everyside except the bottom, and put the shelf on the lower part. I also put some bracing on the bottom part as I did on the top part. Then I used a router to cut out the back opening, and the front door so that the door could be flush mounted since I was going to cover it all with slate, but I never got that far.
