If you want to cull it without it experiencing pain, put the bowl in the freezer. If I have a fish and was not carrying out water changes I would just donate it to someone else.
I'm actually a fish expert. [seriously] I worked in a huge pet store in the fish department ... Dropsy is a VERY painful disease, and there is no cure for it. You can skip the vodka, since goldfish hibernate in the winter, you can justt put him in a butter dish with a little salt ... little being the key word ... and pop the sucker in the freezer overnight. Once the water reaches a certain temperature he'll just go to sleep. Then if your as caring as I am with fish, you can just burry the block of ice, and say your final goodbyes. I'm sorry to hear about your fishy.
