I've built a few tanks using epoxy-and-glass over plywood.
They work great.
For fish tanks I silicone in a side window,
for sumps I don't bother.
I doubt that I'll ever again make an all-glass tank.
My best advice is to google "stitch and glue boatbuilding"
for step-by-step instruction.
It's simple, fast, and cheaper than all-glass tanks.
I found a pretty good guide online called
"2010 FREE Plywood Tank Manual."
There are lots of "DIY plywood fish tank" articles out there,
and some of them are absolute garbage.
I would not want to be around when these disasters are filled with water.
Boats have been built with this technique
for at least a generation now,
and boat builders are nothing if not conservative.
I've built several small boats this way
and have watched my kids sail away in them
without a qualm.
Well, with no fear for the integrity of the boat, at least.
Expecting the world to treat you fairly because you're a nice person
is like expecting a bull not to charge you because you're a vegetarian.