Hi..........had this problem for months now.....two fish both Black Skirt Tetras......originally thought it was popeye from agression damage as my Bueonos Airires chase them......but there wasnt any fin damage. Also the whole eye never popped out........it looks like a normal fish eye but with an air bubble on part of it.....then both eyes on the one fish are like this and one eye on the other fish is also. Plus both of their mouths look like they are bruised......a blackish purple and the damaged eyes are the same color........as for their activity.....they seemd to of never noticed.....i thought gas bubble diseaes also, but there are no bubbles anwhere else on theri body aside from the eyes.........any thoughts id greatly appreciate........thank you...Elated