My 3 yo daughters betta died a little bit ago. It was from being put in tap water (I did treat it, but either it was too cold, too much chlorine, etc.) or a new tank (that may not have been cleaned enough) too quickly. He was barely swimming, not eating, then he started semi floating sideways and upside down. It was about 3 days after the accident that he died. Our tank broke. I also felt guilty because I felt it was my fault. My daughter cried and cried. She still talks about how she misses Mr. Fishy. We told her that it is ok to miss things that we love when they die. We also had a type of funeral for the fish. She got to say goodbye to him and tell him that he was a good fish friend. We referenced the movie Finding Nemo and said that Mr. Fishy needed to go back to the ocean. All drains lead to the ocean in Finding Nemo so flushing him down wasn't as traumatic for her. Good luck. If you get a new tank, I would make sure that you have a stable one. While you are setting it up, mention that we don't want to break this one so we don't hurt our fish. That is part of taking care of animals. I would also start letting him help you feed the fish so he has some ownership in taking care of him.