I know this thread is 7 months old or so, but I wanted to respond for anyone reading it. You can use spray paint on decor or in your tank. You have to use Krylon Fusion brand tho. Its been used my many for a long time in the hobby. Some people let it cure for 24 hours to a week before putting it the tank. I usually let it dry and cure outside a few days, then rinse it really good (so there's no smell), then I put it in the tank. Never had any issues.