DIYish mega stand

Go get this from Lowes or Home depot. It costs about $150 but it holds 1500 lbs per shelf

Set it up with tank height + work space + 1 1/2" spacing between the shelves. I set mine up for 20g longs. I built it in mind for 30gals as well, but I would have to move the shelves for those. I wouldn't go much longer than 30gal though.
Get some 1/2 inch B/C grade outdoor plywood (1-2 sheets) 2-3 8ft lengths of 1x2's eyeball them and try to get the straightest ones. also a can of floor grade outdoor urethane.

Under side of one shelf

Top side of same shelf

Notice the plywood is cut against the grain for strength purposes. You will have to add a filler piece on one side to go the full shelf length. Screw and glue a 1x2 to each long edge. Measure the tanks you are building for and screw and glue your short pieces of 1x2's so that the edges of the tanks will be over them. The screws go in from the plywood side like so.

Give it 2-3 coats of urethane for waterproofing. If stain is desired do so prior to the urethane coats.
It is also recommended to spray paint the metal stand with an epoxy paint to prevent rust.
Line up your tanks so the edges rest over the 1x2's on center. I designed mine for my tanks to be snug up to each other.