I've never seen any issues with tires in a pond. If they're shredded, then you might see a little rust color from the steel belts. We've always drilled holes in them to get rid of any air pockets and allow them to sink if putting them in a full body of water.. Maybe, others on the forum have had a different experience?

--Kevin Mc
It's not about the stomach. It's about the fish. Take care of the fish and the stomach will be fine.