Question
Robyn, hi, thanks for the great info.  I am fairly positive my 3 year old sons giant goldfish that he has had for 2 years has dropsy (after reading your info and looking at photos), he truly looks like a giant pine cone...Where can I get the antibiotics you mentioned on your site?  We have a 10 gallon tank with 4 goldfish, a pleco and a zebra danio.  Only one goldfish seems to be affected.  it is still eating, i think he looks like he is going to burst...
any help would be greatly appreciated.

Answer
I'm sorry about the goldfish.  You can certainly add some antibiotics to the tank.  Fish with dropsy rarely improve but we should still try.

If you are referring to Maracyn I and II, here are links to one place that sells it.  They don't seem to have the pill form anymore:

http://www.thatpetplace.com/pet/prod/236719/product.web

http://www.thatpetplace.com/pet/prod/236721/product.web

Any aquarium store worth it salt should sell salt!  And also, Maracyn I and II by Mardel.  Aquarium salt and Epsom salts can help with dropsy (only use one or the other at the same time).  See http://www.fishpondinfo.com/fishcare/salt.htm for more on salt.

How big are your goldfish?  They must be still pretty small to fit in a 10 gallon tank.  If your pleco is a common sort, he will also grow over a foot long like goldfish too.  I have 3 goldfish and a pleco in a 65 gallon tank; your fish need more room.  The little danio would love some buddies (danios are schooling fish) and to have the goldfish move to another larger tank so they don't decide to eat him one day when they're big.

Good luck!