Umh, hey I don't know a lot about fresh water tanks but, did you cycle your tank before you put in your fish? If not you're going to have to do some major water changes and feed your tank VERY lightly. Feed an amount of food roughly = to the size of your fishe's eye. If you have a friend etc. ,"that you know is clean no infections in the tank etc." see if you can get part of one of their filter pads to start your tank off.
hth
chris
p.s. I really wasn't kidding I know very little about fresh water but, it can't be that different.