I want to change my outdoor waterer with something that looks nicer and blends with the background better. I found some nice natural-looking fake rock and log planters that I want to use for water for my chickens. They are meant for terrariums, so sorta with animals in mind, but not to drink from directly... They are made of polyurethane in the form of a hard foam. Would they be safe for chickens to drink from? Would anything harmful leech into the water? If yes, is there anything I can paint and seal the inside with to make it safe?