I'm recommissioning the stand from my old 40g for this setup. The stand is also DIY and I don't think I've ever posted pics of it so I thought I'd include some pics of the construction.
It's a pretty simple design. I was going for the smooth lines of the ADA-style tanks but wanted wood grain.
Here are the top and bottom frames made from 1X4s:
Sides are 3/4" birch plywood:
Additional 1X4 struts up the side for extra support of the top frame.
Additional back vertical and horizontal pieces added to the back for shear support
Drylok is fish safe but I wouldn't use it to waterproof a plywood tank. I've seen a couple of failed drylok plywood builds. There were a few sections near the top of my paludarium where I used drylok to seal the wood and they started molding and rotting after a few months (and that wasn't even submerged, just high humidity).
Apparently it works better if you put a layer of concrete backer board on top of the plywood and then apply the Drylok over that, but at that point it's probably no longer cheaper. For waterproofing plywood tanks I would stick with the tried and tested epoxy or a liquid rubber product.
very nice job. It looks like the tank sits directly on those 4x1s. I would put plywood between the stand. That makes for a better weight distribution. Maybe even add some foam like a camping mat or styrofoam