It may not pertain here but I've read that the floating syndrom in goldfish (inability to pass the bladder air) is commonly caused by a digestive back-up and pinching of the air ways. I'm vaigue on details but can try dig up the article. One factor was high nitrates, like in the 100s ppm, I think. It makes for lazy digestion an clogging. Again, just general info.
My suggestion is to post on PCF for a higher chance of more professional help.