What’s on purple firefish?

[Uncle_Bob]

Happy new year everyone!

I’ve noticed there is a blister on the side of my firefish as I got it two weeks ago. It ate well and behaved normally in the past weeks, so I didn’t worry too much. However, it suddenly became really weak and didn’t eat today. I was wondering if that’s gas bubble disease? or if anyone can identify what it is and what to do please let me know. Appreciate

 

[Jay Hemdal]

Welcome to Reef2Reef!

Sorry - the picture just isn't clear enough to see what you're describing.

Gas Bubble disease stems from supersaturation of air in the water. All fish would be affected, and it usually shows as silver spots in the fins. I think we can rule that out in this case.

Weak and not eating are of course very serious symptoms of a problem, but I just can't tell you what that might be.

Is the fish breathing deeply/quickly?
Are there other fish in the tank, are they showing symptoms?