My mom used to etch on glass. It was a bit tricky though. You get a stencil and etching chemicals and would then apply it on the OuTsIdE of the tank. That might be a cheaper route to go! She also carved on glass by hand. The tools for this is expensive though (she even carved designs on cars windows).
anyways, here is the link! neat!
http://cgi.ebay.com/29-Gallon-glass-Aquari...1QQcmdZViewItem
If anyone buys it let me know! (I'd like to see a pic of the fish in it too!)
sammie
Ooh, he also says a person can let him know if they would like a different design. goldfish anyone?