HELP! Disease ID

[sandboxes]

See the attached photo.

I'm leaving for the holidays very soon and I need to decide what to with this Tiger Barb. What is this growth just behind his fin? Is it something that I need to isolate him from the rest of my tank?

Thanks in advance!!

 

[Lotus]

It looks like it could possibly be roundworms. Pic here: http://www.fishpalace.org/Disease.html#Worm

I had something similar on one of my fish, but I just ate, so I won't describe it. Treat the whole tank with an antiparasitic med if it seems like it is roundworms.