Don't puncture the air bladder, I think you will just be asking for infection. Try putting a weighted plastic collander or Sterilite with drilled holes on the bottom, keeping him from the surface. If he is not infected (swim bladder disease) he should burp it out himself within a day or so. If it is something more serious, I don't think a puncture wound will help, and you should do a search on swim bladder disease. Treatment and cause are not really straightforward. I lost a magnificent foxface to this, it didn't respond to anything I tried, including antibiotic injections by a vet (finally, after a lot of other things were tried).