I have a 5 yr old Moonlight that is struggling after changing his tank Saturday (10/28). He is vigorously swimming downward but remains pretty much in the same position, occasionally swims to the surface for a breath of air, belly appears slightly extended, scales still appear smooth, no appetite and if he does swim other than downward he appears somewhat unbalanced. He has NEVER had any illness so I am unfamiliar with what may be wrong but it appears that he is suffering.