I had posted a few days ago about my tetra not eating. He was the sole
survivor out of a group of 5. Interestingly enough, I bought a few
more tetras today (neons and zebras), and he immediately perked up and
ate with the community. I guess it was just loneliness.

It's worth noting that he has lost some of his color, which I didn't
notice until he was side-by-side with others. But since he's eating
and swimming around, I'm hoping that it will come back.

Anyway, one of the neons that I bought was apparently damaged pretty
badly by the guy removing them from the tank (a clueless guy at
PetSmart). I didn't realize it until I got him home, but almost the
entire tailfin is gone! There are a few "sprigs" remaining, but that's
it. The poor little guy can barely keep himself upright, much less
move around enough to eat.

Any suggestions on how to treat him? How long (if ever) will it take
for new tailfins to grow in?

TIA,

Mike