One of my tiger barbs lost his fins

[JoLy]

I should of had more of them...  will they grow back?

[dan2x38]

how many in the tank? how big is the tank? fins do grow back but if the tank is small and a small shoal they will pick on him... fish will chase the weak ones especially tigers.

[JoLy]

It's a 10g and I only have 3... I'm buying 4 more asap

I isolated the injured fish from the rest of the aquarium to insure that he can eat and doesn't get attacked.

[dan2x38]

That is a really to small a tank for tiber barbs: http://www.aquaticcommunity.com/barbs/tigerbarb.php IMO I would not put them in less than a 29g. yes you need a large shoal or they will rip each other up.

[washefuzzy]

Salt in the water will help the fins heal up nicely.

[sas]

I should of had more of them...  will they grow back?

If the fin was only partially damaged it will grow back, with good water parameters and no stress.
But if the fin was actually pulled off the body, there's a good chance it will not grow back since the base of the fin will have been damaged.
I have a clown loach that is an amputee and if you didn't know about the missing fin you couldn't tell, unless they really looked carefully. This guy is thriving and growing well.

[Fishnut]

Yes, 10 gllons is too small for a group of Tiger Barbs.  If you haven't gone out to get them yet, don't.  They can get to be more than 2" and are not the nicest fish. When they're confined to a small space, they get even more unfriendly. The finless one was likely a weak one and they decided to get rid of it before it weakened the school.

If you add 1tbsp of aquarium salt per 5 gallons of water to the hospital tank and keep the finless fish in good water conditions, then it will be abe to heal and hopefully grow back the fins.

10 Gallon tanks are meant for small peaceful fish like white clouds, tetras, guppies, etc.  All you have room for is 10 fish that grow to be a max of 1 inch...friendly fish.