Banggai Cardinal getting darker and hiding

[CloudReefer]

Hello, I have a bonded pair of farm bred Banggai's. They were tiny when I got them and have grown a bunch, though one has grown significantly larger than the other. They've gotten on great for the last 8 months.

Recently, the smaller of the pair has started getting much darker, mostly on it's left side, around it's stomach and towards it's tail. It's been hiding a lot (especially likes to hide near the powerheads) and not eating that I've seen. It seems to be swimming fine, and is responsive and alert. My other cardinal is fine and acting normally.

No sign of fighting, no sign of disease. All other fish are doing well.

Any thoughts?

 

[MnFish1]

A picture would be great - under white lighting. A darkening on one side would be somewhat odd for a parasite - How old would you think your fish is>. Have you added anything else to the tank that could be a disease carrier? Could it be breathing breeding coloration? Other symptoms? Other fish sick?

 

[Jay Hemdal]

I just ran a longevity study on public aquarium Banggai cardinals - on average, they only lived 1.8 years in captivity. this was a lot less than I would have guessed. While your fish is younger than that, it still is "in the curve" for coming down with some chronic issue like mycobacterium.