I had some clay pots that were previously used in one of my tanks. They hadnt been in water for about 2 months and were sitting in a box in my garage. So before my kids softball game I decided to give them a good rinse and drop them in. When I returned a few hours later, I had found $200 worth of fish dead and the remaining fish left gasping for air on the surface. I immediately pulled the pots out and added a heavy duty air pump and within 5 mins, all the other fish began to come back down to their normal tank spots. So what do you think? Has this ever happened to anyone else?