He could just be bit stressed from tank revamp but on the other hand you should test the water in your tank for ammonia, nitrite and nitrate. Did you do a complete water change on your tank and if so, did you cycle the tank b4 placing him back in?
Also, gravel can be bad for axies, when they swallow it, which they will eventually do (esp. as they get bigger and snuffle), it can block them up and cause blockage problems and stress your axie. You'd do better to replace with sand, which can be bought from Bunnings or other hardware/landscaping places quite cheaply; or alternatively, bare/no substrate or large pieces of slate/rock.
How big is your tank?
Can you post a photo of the fluffy stuff on her gills (they're not feathers, but we all know what you mean)? I would have thought it was fungus from the description but as its only been a few hours maybe its something else?
(Message edited by kapo on September 16, 2006)