GE Silicon I is safe, GE Silicon II will poison the tank. The type II contains an anti-mildew agent that can leech into the water. Regardless of type, let it stand for at least 48 hours before getting it wet so it has time to cure.
BTW, Dow Corning makes All Glass-http://www.americanaquariumproducts.com/AquariumSilicone.html