Gaping hole in jaw...

[Dustmite]

...and it wasn't the mouth! I bought four Buenos Aires tetra about two and a half weeks ago and they were doing great in the tank. About a week ago, I noticed that one of them had developed a bit of a swollen jaw, but I didn't think much of it. I just chalked it up to the fish getting a little overaggressive eating and bumping into something. The next day, I found that there was a hole in his jaw developing just below the mouth, and by the next day it ended up being three times the size of his mouth. I began treating with Melafix because I thought it may be some kind of mouth fungus (internet searching for a disgnosis proved unsuccessful). He was still as active as his healthy days, eating just as well, even taking in food through his new orifice! He lasted through five days of treatment and then just up and died without warning. Does anyone have any idea what could have caused this? I'm including two pictures of the ailment. ~Jake

[MadridKid]

My guess would've been he was attacked by some other fish, but for a disease of some sort to cause that damage so quickly, i would have all ready excluded that option. You shouldve seen some symptoms at the store or when you first got them right?

[Dustmite]

There was nothing wrong with him at the store, and his behavior was absolutely normal up until death, despite the huge hole in his face. I really don't think it was a wound; the jaw swelled up a bit at the front, and then the next day it opened up. In addition, there's nothing in my tank that really could have attacked him and caused this.

[MissFishy]

That is definitely odd on a tetra. Something like hole in the head disease almost...could be something bacterial or a parasite. Look carefully to see if any other fish are showing any symptoms anywhere on their bodies. What were you treating with?

[Dustmite]

The three other tetra are perfect. I began treating with Melafix right after the hole developed; I thought that it may have been a mouth fungus, and no information that I found online could tell me for sure what this was. He lasted five days on the treatment and remained just as active as before this all developed, but he never showed any signs of improvement.