Here is a large bench I built using only a miter saw, clamps, screws and glue. Very simple construction and very very strong. The top is a solid wood exterior door unfinished.
Try googling DIY reloading benches. I also have my current aquarium setup on a 2x4 construction, but its built into a wall and semi-finished so not as clear of a visual example.
For an aquarium I would just put the ring on top of the legs and run some boards across the center for added support and maybe center legs if you have a large aquarium like 75+ gallons. Then again if you look at the stands for 150g tanks they sell at pet$mart my stand would probably hold the Georgia aquariums largest tank.