I have had a shubunkin for about a year who seemed fine until I noticed he
had a on his tail about the size of a ball-point pen tip. (He was really
tame so it was easy to closely examine him in the pond.)

I took him inside to a 20 gallon and started to treat with a "broad
spectrum" fish medicine. I did not recognise the active ingredient: it
was some huge organic about 60 characters long.

The fish continued to develop 2 to three more lumps. It also was eating
heartily until the day it died and was not at all emaciated. The only
unusual behavior was that it started to sit on the bottom the last 2 days
before death.

There are at least 3 species of small(2cm) snails in the pond: ramshorn,
a fist-shaped snail, and a pointy-looking snail.

This guy was my last goldfish, the others having already been eaten by
birds. I'm just letting the plants grow and watching thousands of tadpoles
slowly devour them.

Does anybody know what happened to the last shubunkin?