I have a 55gallon tank that has been established for over a year. I decided Saturday to redecorate. Added new gravel, plants and decor. Everything was rinsed. I done a 50% water change also. I left the fish in the tank. I couldn't catch them, so to avoid stressing them anymore I left them alone. The water was cloudy Saturday night. I did treat the water because we have city water, and I didn't fill the tank all the way up just enough to get my filter going. Woke up Sunday and the fish had begun to slowly die. This morning my Pleco was fine. I did not see my 2 corydoras but I did see their 1 baby. What did I do wrong? Is there anything I can do to fix the water? Thanks