Question
I have one fish,out 11,that is so swollen that it looks as though it will burst.The pond is well established,14 years,the affected fish eats o.k. and does not look distressed.The fish has had this condition for a few months.Any ideas?

Answer
I'm sorry about your fish.  If the scales are sticking out, it's dropsy.  If the fish grew fatter slowly, it's probably related to kidney malfuction.  Basically, the fish can't pump out the water that naturally floods into its body.  Neither dropsy or kidney problems are easily treated.  You can add pond salt to the pond to help at 0.05% if you have plants and twice that if you don't.  That will only relieve the pressure a little bit.  Antibiotics are usually suggested but also have little impact.  If they can be injected, that's the best chance for improvement.  I have photos of fish with dropsy and kidney problems on these two pages:
http://www.fishpondinfo.com/fishcare/dropphoto.htm
http://www.fishpondinfo.com/fishcare/bigphoto.htm

I wish I had better news.  Such fish do eventually have too many cells in their bodies that rupture to survive but it can takes weeks or months.  Luckily, it's not contagious.  Any bacteria that might be involved are ubiquitous which means they're always there, and only weakened fish get sick from them.  Over the years, I've had half a dozen fish become grossly enlarged.  They lived like that for quite a while and treatments did nothing.  Searching for dropsy will give you more tips on treatment.  Treatment for dropsy would pretty much be the same as for kidney malfunction.  Basically, dropsy is a fast internal bacterial infection that causes kidney malfuction.  Fish with dropsy don't live as long as those with just kidney problems.

Good luck.  I hope your other animals are safe and happy!