I would like to build a beach area inside of my 7g tank for my lil juveniles...anyone know what type of plastic or acrylic I can use to make a divide to fill with sand and peat moss??
Plexiglass would work. Use GE Silicone 1. Safe for use in aquariums/Fish. It no longer says so on the tube, though. They now sell this for an insane amount in a tiny tube and other manufacturer's name on it, targeted specifically at the fish hobbyist.
Be sure to buy GE silicone 1 and not 2 or 1*. It's for Windows and Doors. Not Bathroom/Showers. The latter has a mold preventative of some sort. You don't want that. Allow to cure for a couple days. Here's some info if you'd like to read further... http://www.cichlid-forum.com/phpBB/viewtopic.php?t=21234
2 days should be OK. It will have a strong odor, especially initially. Caulk it in, put it outside somewhere it won't get wet to Air out and you should be good. I've personally used GE1. It's totally safe.