From what I've read I'd steer clear of anything "painted" unless you know for sure it had a tag on it that said "aquarium safe". Even some plastics can leach toxins into your tank water.
If you got it at Petsmart or Petco perhaps you can still find it on their website and it should tell you what it was made safe for. Just a thought.
I believe that most ornaments made for hermit crab/reptile tanks are NOT aquarium safe. You'd be better off buying something new that you know for SURE is aquarium safe.