Need some input on water proofing

[snowkick]

I am currently building a vivarium for some california newts and have gotten stuck as too what to use to make sure the sturtures are completely water proof but also safe for the newts. I know silicone works but my tank is rather large and would cost alot to cover the whole structure with it. I looked at a website and they recommended shields all water sealant, however I looked up the price to order this and it will cost just as much to ship the stuff and is cost to buy it. Wondering what other people use to water proof their custom structures that I might be able to pick up at local hardware store?? Thanks for your input!!

[beckdg]

pond coat, pond armour, west systems epoxy paint, 2 part epoxy paint for potable water sources, famowood glaze coat...