It all starts with metal square tubing \m/:

and welding:

painted with silver-ish paint:

oh, and we need wooden floors. Now it is time to cut some corners ;)

Paint again:

The rear wood panel gives it additional strength to not bend sideways. It hides the pump/filter, light power supply etc.. I'll add a door for the "tech room" later. Holes will be drilled in the top plate to let the LED light power cord and water in/out thru.

Counter-sunk screws from below hold the wood parts in place. This further stiffens the construction.

It is mounted "free standing" against a wall and can support 400kg+ of people standing/sitting/riding on it, so it supports the aquarium as well. The lower areas can be used as book shelfs etc. (still some small particles in the water from filling the aquarium in this pic):

As the water is transparent, the whole thing is as lightweight as possible. Look - there are fish swimming around the table!