CichlidFish.com - Fish That Think.

It sounds like chronic dropsy, a slow developing bloat. Generally it has two cause's, one is an internal parasite. The other is a cancer, or organ tumour.
Since you have run the gauntlet of meds I am voting with the cancer, as the cause. Unfortunatly, there is no cure, if its cancer,
more a mater of how long the fish seems to have its quality of life.
In some case's of cancer,so I have read, it can be passed on to other fish. However I am not actually privy to any real case of the cancer infecting other fish in a tank.

Samm

I agree, but in the long run, it was the better choice. Its never an easy situation. I should have pointed out that there is a very informative thread in our FAQ's regrading euthinazia. Hopefully you will not have another situation where you you need to use it, yet I might recommend you read it, and I think anyone else who has fish should read it as well. Unfortunatly, its a situation many fishkeepers will someday have to face.