Question
I think one, maybe two, of my pond fish have this and another died before the winter of the same thing. They float at odd angles and look dead but swim off if I try to net them. Pine cone appearance is evident. Is it infectious, should I treat the whole pond even though the others (about 30 fish) aren't affected? Thanks

Answer
I'm sorry about your fish.  Dropsy is usually caused by ubiquitous bacteria in the pond.  That means, they are bacteria that are normally in the pond.  The fish then only get sick with dropsy if something is otherwise wrong such as an infection, poor water quality (be sure to check your pH, hardness, ammonia, and nitrite; do a partial water change with added dechlorinator; add some fresh activated carbon to the filter to remove any toxins), and so on.  So, while it's technically contagious, those bacteria are already in the water, and your other fish have already been exposed.  That doesn't mean though that they will develop dropsy.  I suggest adding pond salt at 0.05% to the pond if you haven't already.  Also, add good bacteria.  They help clean up the debris in the pond and reduce pathogenic bacterial counts.  I recommend BZT Aquaculture and KoiZyme (ask me if you want more details).  Dropsy is rarely cureable.  Salts and antibiotics may have minimal affect.  The only fish I've known to be cured were injected with antibiotics which requires a vet (for the needles and medication which is normally liquid Baytril).  I don't think you should put in a true antibiotic at this point as it would be expensive and potentially kill your good bacteria.  You can, however, add all natural MelaFix by Aquarium Pharmaceuticals which reduces the bad bacteria levels.  The only concern is that it lowers the oxygen but, if you aerate the water well during treatment, the oxygen levels should be fine.

Good luck!