First off, it looks great! One thing I would reconsider, however, is the placement of the horizontal crossmembers at the top of the stand (unless the stand is upside-down in the picture). To get the best strength out of the stand, you'll want to transfer as much weight into the vertical boards. The way the horizontal crossmembers are screwed into the vertical members, the loads are only being supported by the small diameter of the screw, which is the weakest part of the joint. You may consider having the horizontal beams sit on top of the vertical beams instead of being screwed into the sides. It may be a little work, but not doing so may lead to inconsistent support, which can be a tank buster (especially if you use glass, but I cant remember what this tank was to be made from).