Sounds like it could be ph shock.
How long did you climatise the fish for, what was the ph of the lfs to your tank.
pH Shock
As its name suggests this condition occurs when a fish is introduced to quickly into a new environment which has a very different pH from the one it came from, when the pH is adjusted to quickly and the fish have little or no time to adjust themselves, or when the pH is to far outside the fishes normal range.
It is very important that any change in water chemistry is made slowly and fish should never be exposed to changes of pH greater than 0.5 of one unit on the pH scale in either direction.
Avoidance is by far the best solution because in most cases the symptoms don't appear until the second or third day by which time the damage has been done and the fish will probably die.
A fish suffering from this condition will show all the typical signs of shock -
Lying on the bottom and paying little or no attention to its surroundings and ignoring potential threats.
It may even lay on its side or go upside down completely.
There could be other signs to, related to Acidosis and Alkalosis
Excessive mucus production.
Rapid breathing.
Swollen abdomen. (Alkalosis only).
If the condition is allowed to go on for one or two days then the chances of a successful remedy are greatly reduced because a lot of damage will have taken place. If the symptoms are spotted early enough there are a couple of things that will help.
Begin to return the pH to the original pH in steps of 0.4 of one unit on the pH scale and allow 3 hrs in between the adjustments. Make these adjustments until the pH is returned to a safe and satisfactory level.
Treat the tank with a broad spectrum anti-Bacteria/Fungus compound to prevent secondary infections of the Skin and Gills.
Prevention is easy. A successful treatment isn't!
