Steel stand design help?

[EnderG60]

Im looking to make some metal stands for my new tank(350 gal) and frag(320 gal) system. I plan to use 2" square tube, but since Ive never used metal before for a stand I dont know how many support legs are required.

Can anyone give me an idea of how I can make sure I have enough support?

 

[mcgyvr]

What wall thickness tube?
11ga every 2ft should be plenty.. But specific construction techniques also come into play