The reasons for this situation may be the following, a sudden change of water, two, the water has not been treated, 3 water temperature and the original water temperature difference is very large, 4 eat more, 5 water quality problems, 6 enteritis, solution, alone get out of that one, put in a pot, the water should not be deep, just did not pass the fish shall prevail, do not feed, after a few hours to see the color of its stool, if it is white and mucus, is enteritis, then add some hyoscine to the water, change the water every day, then add medicine, it is estimated that three or four days will be fine, but the water is not deep enough. It is enteritis, then add some oxytetracycline to the water, change the water every day, and then add drugs, it is estimated that three or four days, if there is no abnormality in the stool, it may be a side-turning, it is in shallow water for a few days, to see if it can be cured, side-turning into a variety of types, it is not easy to cure, try the simplest way to it, if the three or four days into the deep water is still not working then, then let it die on its own. !!!!