acrylic craft paint should be ok also, someone correct me if i'm wrong though. I have a 55 gallon paludarium. It has a "creek" with running water going into a little pond that has a betta in it.... he's been in there for over a month now and seems healthy as ever... The creek area is made of great stuff foam and was first covered in mortar, and then painted with acrylic. There is also some foam painted with acrylic in the pond itself, and it seems to be holding up to the water very well also.
1 10 gal low tech planted tank. 1- 10 gal lowtech w/ diy co2. 55 gal lowtech planted tank. 20 gallon reef tank. 55 gallon paludarium for dart frogs. large exo-terra vivarium for madagascar giant day gecko. working on getting 65 gal brackish tank soon