Clove Oil: Use at a dosage of 0.25 ml per liter of water. Shake mixture vigorously. Add fish immediately, before the oil has a chance to separate. Once the fish is deeply anesthetized (does not twitch with gentle prodding, and no gill movement is observed), add lots of crushed ice to the water.
Found on another thread. :P This quote by redbettagirl.
Yes, QT them, wait a while to add anything back to that tank. Tear it apart, wash everything, and then add the otos back. Watch them for a few weeks and if they seem alright, get another fish.
And roadrunner, that is very incorrect, that will be a cruel and inhumane death- it will not sleep and freeze like you or I, it will be alive until its cells explode from the cold, experiencing great pain all the while. Please do not use this method to euthanize your fish.
The cold shock method is different from freezing the fish; I'm not sure if that is what roadrunner was referring to....With the cold shock method, you place the fish in almost frozen water. The fish doesn't freeze, rather it dies quickly from shock of the sudden temperature change. This is a very controversial method, but often not considered as bad as placing a fish in the freezer. Blunt-force trauma and decapitation are the most accepted commoly-practiced forms of euthanasia. Clove oil isn't on the AVMA's list of humane euthanasia methods, largely because of lack of testing, but it does anaesthetize the fish before it dies. Clove oil is the method I would use because of the controversial claims about cold shock, and the fact that I could never bring myself to crush or decaptitate a fish :(
How long has the fish had dropsy? It's rare that a fish will recover, but it has happened before. If he's not suffering, your friend could do an epsom salt treatment to see if it helps. If the fish is suffering though, euthanasia is the most humane option.