I've built a few stands with canopies before ranging from a 240 to a 480. All were made out of 3/4" OAK veneer and were made with only a circular saw, jig saw and a hand saw miter box. The miter box was used for cutting the oak moulding.
For the front of the stand, I used the jig saw to cut out the door openings. A circular saw could have been used as well. Those pieces I cut out were later used for the doors themselves. I just took some 1x2" oak and made a frame for the doors that overlaid the edges of the cuts. This hid any imperfect cut lines and also provided a clean stop for the doors. In hind site, I think I did use a router to bevel the edges of the oak trim but you could always pick up some beveled 1x2" oak pieces from a hardwood source or even some nice mouldings.
In the end, the stands and canopies turned out great and were very cost effective and sturdy. For a tank your size, no 2x4 support should be needed as 3/4 oak veneer plywood is very strong.
These are some old pictures from 1992 I think and are the only ones I have of the stands but the pictures themselves are cherished memories which should be no surprise given their nature.. Enjoy and maybe it will give you some ideas for your stand.
This one you can see the stand an canopy.
I know this picture is nuts.. It's amazing what some liquid courage on a drunken birthday will do. I'm posting it so you can get an idea of how the doors were built as this is the only picture I have with the doors open. It was a very simple build and was completed in one day including stain and brushed on clear coat.