Just wondring if these #6 polystyrene solo Cups are safe to put in a saltwater tank. Mainly for a qt tank for hiding places since I don't have pvc and don't have time to get it. Want as little stress as possible so I want to give them hiding places and it looks cool to add some character to the qt tank. Not that it's for looks haha.just want to know if it'll leech anything in or be affected by the copper treatment.