I have 3 female gold dust mollies in a 20 gallon tank. I started the tank about 6 weeks ago. I believe the tank has cycled, the ammonia was pretty high for awhile and then slowly started to come down and is now back at 0. The problem is one of my fish was at the bottom of the tank most the day. It can still swim around but has been hiding out at the bottom. Is it sick? Any suggestions appreciated. We were just about to buy some more fish but I think we will wait to see what happens now.