Barb in danger of dieing

[Sefu]

About 2 weeks ago, i purchased several barbs at my LFS.

I got 2 Green Tiger barbs and 1 Regular tiger barb.

The regular tiger barb that i purchased is now unable to swim correctly
It doesn't use it's tail at all, only the flipper arms, he swims at a 45 degree angle..

The other barbs that i have in my tank are biting at his Anal part and i see some red startnig to develope in the anal region..

What is going on!

Also, I think i should have paid more attention to the fish i was purchasing because half of one of it's tails is gone.. You know how the tail has a < shape well now it looks like a L its not same size as other side..

I think this fish is suffering alot.. I need help ASAP...

Current dwellers:

4 Albino Tiger barbs
3 Regular Tiger Barbs
3 Green Tiger barbs

 

[Jen]

Well, barbs are schooling fish and like to be in groups. Most people around here will tell you 6 or more to keep from attacking other fish... and being less agressive to their own kind. Now I see that you only have tiger barbs in there, so never mind.

Do you have lots of hiding spaces? What are the water parameters at? Do any of them look sick? How big is your tank, how long has it been running? All of these questions will help us try and figure out what is going on with your fish.

 

[Sefu]

I have plenty of hiding spaces

As for the water, the last time i checked it was about a week ago, and it was tested by my LFS. Everything was fine but the Nitrite (or nitrate I forget ), the woman said to have a water change every 2-3 days and it will be fine..

As for the tank size its 20 gallon

All the other barbs seem to be healthy, swimming around chasing each other.. Normal Behavior.

My tank has been running for several months.

It just hibernates in a corner now .. the sick/scared Tiger barb.