Green Barb isnt eating

Question
Dear David,

I recently introduced three fish into my tank - it's a small tank (30 litres) so is
not that densely populated, but my cory was lonely.  I got another cory to
keep it company, and two green barbs.

The new cory is fine (the old one was delighted to have a companion other
than his reflection scuttling along the bottom of the tank!) but I'm having
problems with the barbs.  One was very aggressive and bullied the other -
the bullied fish seemed fine and just avoided the aggressive one, but when it
came to feeding time the aggressive fish actively looked for the other fish to
victimize.  Ironically, the aggressive fish was too busy chasing and nipping
the other one to stop and eat.  The bullied fish would just swim off and grab
at food as it fell, so it was fine, but the aggressive one hadn't eaten for quite
a few days.

The (formerly) aggressive fish is now weakened - when at rest it often hangs
vertically, nose downwards.  It seems confused as to why the other fish is
now stronger than it is (ie it attempts feeble aggressive moves and then runs
away when the other responds) and it just wont eat.  It gets excited at feeding
time just like all the other fish, but then ignores/misses all the flake food that
goes past it.

I don't want to isolate the fish, as moving it would stress it out, but is there
anything I can do for it?

Answer
Barbs need to be in shoals of about six or more to function well in the aquarium tank.  They can be aggressive as you have seen or they can be very affectionate tank mates.  I would try to introduce a few more barbs to the tank.  I would also dose the tank with salt per its instruction label. The weakened barb may eat if you offer something like tubiworms.  If you feel as though you would like to medicate the tank then I would use a half dose of triple sulfate.   dave