I have seen a few about on the net.
What i would do is build three pillars as high as you want the tank, while building turn four bricks around to make shelving studs to sit the shelf on.
For the top build a frame out of 2*3 or 2*4 inch softwood with a ply base, to sit on top of the brick pillars and use some 5*1 softwood to make a trim to cover the frame and base of the tank.
Then you could make a couple of frames to sit in the brick work opening to take a couple doors,
If you have a concrete floor your singing, but if you have a boarded floor, you will have to take the boards up and put a small foundation for each pillar, then batton up and replace the floorboards after.
sharp tooth....a 5ft tank wont need such a massive stand. unless you really just want he look of brick then i would just buy some 2x2 timber and build your own.
Personally I'm with sharp tooth, and would go for somethings along the lines of these links, just modify and stamp the with your own personality
Just build onto the wall, that way you could save on materials for back etc.
http
/www.fishforums.net/index.php?showtopic=110738
Here is a different idea same principle, all you would need it one or two ends.
http
/www.fishforums.net/index.php?showtopic=117673&hl=
Keep us posted
regard
Simon