I performed a major clean and WC last night since I'll be leaving for a week and I don't want our pet sitter having to worry about anything other than giving the already sorted and labeled food, and making sure the filters/heaters are working. After I was done, one of my Cardinal Tetras seemed to have swim bladder issues because he was floating belly-up when he wasn't actively swimming and floated back up to the top when he stopped. I isolated him in a hospital tank in case he didn't make it till morning. I slowly raised the temp to 80F, added an airstone and then just watched him closely. Within 2 hours of the WC he started to act normal again and didn't seem to have any troubles controlling himself, so I put him back in the main tank. When I checked this morning he had already joined the rest of his school. So was it really swim bladder issues, or maybe he was experiencing some shock from the WC? Everyone else was acting normal.