You can get away with out epoxy paint by using fiberglass resin.
Here's a link to the 137 gallon freshwater tank I made last spring using 1/4 inch glass, 3/4 inch plywood and fiberglass resin. I have little to no bowing with the crossbrace. It's an early picture, I have finished the stand and have the tank trimmed now.
http://homepages.paradise.net.nz/gru.../Kenstank.html