I just received Killer Gil from a friend a few weeks ago. She got him at a local pet store and all they told her was to feed him twice a day and clean his bowl every two weeks. He was a very happy fish! He ate regularly and would always swim up to greet me. Naturally, I changed his water yesterday. I let the water sit for about 8 hours so it would be the same temperature. Now that he has been in the water for about 24 hours he seems extremely lethargic, isn't eating and is layin on the bottom breathing heavily. He looks miserable! I'm in tears because I don't know what is wrong or how I can help him. I'm new to fish parenting and I'm afraid he's going to die. Please help!!!