I need someone to do some welding

[AndyL]

Assuming it's at 1/8" wall HSS (actually .120 but you probably don't have dial calipers); quite honestly you shouldn't need to reinforce this stand.

Deflection (assuming 8' tank) would be 1/16" at center. Assuming 3420lbs (18lb/gal - should be high, realistic is usually 14-15lb/gal); you've still got a ~20% fudge factor before you're anywhere near the breaking point where you'd need to be looking at reinforcement.

Then again there's no real price on peace of mind, thus... Reinforce if you really wish.

Hey whaddya know; stuff I do at work occasionally translates to important things like fish tanks