That's the same plan I used and many others use for their stands. It is more than strong enough for your tank. I would suggest skinning at least the back with some thin plywood to prevent it from wracking (swaying side to side)
i would add a few cross 2x4's on the sides, i like to over build a little just to be on safe side with some extra braces, also are you plywooding this stand?
add a few cross braces onboth sides at a 45 degree angle from corner to corner and the plywood will definitley help with sturdyness of the stand.
I wouldn't use anything like that. Remember we are dealing with saltwater. Metal like that will not last long at all. You will be surprised what some 1/4" ply wood on the back and sides will do.Like these?
i cut 2x4's when i built my stand and screwed it in, 8-10 inches long and 45 degreee both ends of that and put it in all 4 corners on each side and screw it in, like i said i over build but i like to be safe than sorry. where are you located?