dying needlefish?

Question
My daughter (17) is trying to start a new hobby, having fish. For her birthday (2 days ago) a friend brought her a needlefish.  she already had a 30 gallon tank, with 8 or 9 goldfish, and 1 Jack Dempsy.  She added a tank divider to separate the goldfish from the Dempsy, and added the needlefish to the Dempsy side.  When she got up this morning, the needlefish appears to be trying to die.  He will be belly-up for several minutes, still breathing, dart up to the top, and go to the bottom again.  he still has some strength, but it seems to exert him.  Anyway, I called the pet store who told me to take the neelefish out of the tank with the goldfish (too much ammonia) and put him by himself.  I did this.  Of course, he is still acting the same, but am I wasting my time? or is there a chance he can survive.  I told her that they aren't very expensive, that we can replace him, but of course, he was her gift, and she feels guilty if he dies. What should I do??  I am a nurse, so she thinks I can save the life of any living thing.  :)  Thanks for your help!
Amy

Answer
Amy,
odds are the dempsy had something to do with this condition.
If there are no visible marks, I would guess there is a malfunction of the swim bladder, not much you can do.
The dempsy could have rammed him as they do, or tried to eat him either way, not good.
Needlefish really are carnivores and require live food, they will not survive on flake food, sometimes you can coax them into eating from you hand.
The majority are brackish waterfish although they are called freshwater needlefish.
They should have a seperate tank as they combination that you had dempsy, goldfish and needlefish are really not compatable in the long term.
As to his survival I would doubt that he will recover.
Maybe a good time to find a new petshop as the people at the one you are dealing with should have made you aware of these facts at the time of the purchase.
If you have further questions, just ask