At the stone yard I saw pictures of a fireplace installation done in slate that had rough cedar shelving that looked very sharp. I proposed using that as accent and additional support in the way of 4x4" base trim around the aquarium. It could cover the plastic trim already on the aquarium and distribute the weight of the aquarium a little better.
While this idea seemed fairly straightforward at the time, the cuts it required were quite challenging. After two days of table saw, jig saw, chisel, and router, here is the finished result:
Did I mention there will be no visible hardware? That is probably what made it more complicated. Someone later suggested old style iron hardware would have looked good, but it was too late then.
So next I screwed the back piece to the cubes so they stayed in position.
Because the Cedar would fully enclose the plastic trim, the aquarium would need to be placed on the back piece and then the other pieces assembled around it. Yet another idea that seemed good at the time! But first, it was important to make access holes for the drilled filter holes in the aquarium.
Because it's a freshwater tank, I didn't think dual overflows were necessary so removed one to allow for a nice rock background.
And then came wrestling the aquarium up on the stand...
And here it is. I put a couple 2x4's on the front temporarily until I can get some metal brackets to reinforce it. Because of the way it has to be assembled, I couldn't affix the front piece to the stand in any other way.