I've made a fiberglass water storage on a sailboat and have sailing friends who been drinking out of fiberglassed stored water for years. The folks at friendly aquaponics have a free down load that spells out all the joys and difficulties of making a fiberglass tank including what resins to use and not use.
Here the link http://www.friendlyaquaponics.com/fr...ree-downloads/
Also if you do a search on DIY fiberglass tanks you will find a bunch of aquarium enthusiast who have made some pretty large tanks like this one here http://www.brentsmith-photography.co...berglass-build
Of course for our purposes we most likely wont have a glass viewing window