Ok... Formaldehyde (Formalin) is used to treat parasites and Methanol is appranantly added to formalin to keep the formalin in a "fish safe" form. Formalin also kills off your bio-filter. Your tank looks like it could be overstocked to me and you do have nitrites present (should be 0) - I would keep a close eye on that especially since you've been treating with formalin. Info on the formalin/methanol from
http://www.marineaquariumadvice.com/...nd_or_foe.html
I still still think you should try treating for bacterial infection - here is a snippet of info from the fish doc website.. notice some of it is goldfish specific -
Quote:
However, before diagnosing all equilibrium problems as swim-bladder disease, we should be aware that there are other conditions which can cause buoyancy problems. Disease in other organs such as kidneys and intestines for example can also cause problems. This can happen if there is any swelling of the affected organs leading to either a change in organ density or pressure being put on the swim-bladder. This is often a problem with fancy goldfish whose abdominal cavity is tightly packed.
Treatment is difficult, mainly because it is virtually impossible to diagnose the cause and secondly there are only a few conditions that will respond to treatment. It is always worth considering a course of antibiotic injections in case a bacterial infection is involved. An attempt should be made to see whether the fish is defecating, in case the problem is being caused by an intestinal blockage. If this is suspected it is worth either trying to feed the fish a few frozen peas, which act as a laxative, or else try baths in Epsom salts (70g / litre for 5 minutes) which has the same effect.
If these treatments do not work, there is little else that can be done. There is some work being carried out on exploratory surgery, but there are very few veterinarians undertaking this "cutting edge" procedure.
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(taken from
http://www.fishdoc.co.uk/FAQ.htm#equillibrium)