I've seen heavily rocked 90s on stands made of little more than particle board. It's amazing to me how little is actually required to support all that weight. Those will be fine, I'm sure. And they look great, nice and simple but not at all cheap.
I'm curious to know what size and kind of wood you used for the trim along the top of the stand (that surrounds the bottom of the tank) and how you attached it. I am likely going to be making a dresser-top addition that will allow my dresser, at 72x18 exactly, to hold a 72x18 tank (which overlaps it a bit due to the trim), and I'll be using a trim border like that to conceal the edges of the plywood that'll sit atop the dresser. Just wondering what you used for it.