After my goldfish are moved into a pond I want to teach them some tricks, like going through a ring, pushing a ball through a hoop, soccer, fetch, little things like that. I was wondering what I could use for a ring that wouldn't be dangerous. Like would a plastic bracelet (they're small enough right now that that would work) be ok? Or could the plastic potentially have something in it that could leech into the water? Are ping pong balls safe?