question about bala shark

Question
We have a 55 gallon tank and have a bala shark that is acting wierd.  It twitches and swims on his head.  Sometimes he seems to be just fine and will swim normally but generally spends most of the day vertical.  We have several other fish including another larger bala and they seem to be all fine.  We had our water tested and pet smart and everything was fine.  I have been researching this all morning and have found serval sites that say that it could be ich or bladder disease or too small of a tank.  The shark is pretty small still maybe on an inch and a half long so I don't think the tank it too small yet.  We are still new at having a larger tank and learing everyday so we really appreciate the help!!! Thank you

Answer
jamiemae,
the tank is plenty big enough at this point for the bala shark.
it is difficult to say without actually observing the fish but I think we can rule out ick as the other fish would be effected and it would appear on the fish looking like small grains of salt.
It may be a swim bladder issue or it could be a parasitic gill infection as well.
if the latter the gill tissue would be inflamed so check that if you can get a look.
If I had to bet, I would go with the swim bladder issue, hard to tell exactly what issue it is.
you could isolate the bala and watch to see what develops or frankly, you can just leave it be.
i would tend at this point to leave it as it is and just watch, its not a good practice to treat the whole tank for one fish, so if you have a quarrentine tank you may want to put her in there and if treatment is needed thats the place to do it.
I wish there was a magic bullet for this but there is not however alot of the times the fish recovers on its own.
hope things work out.