So, as I've mentioned, the fish are called Fish, Fish, Fish and Bob. Fish #1, Fish #2, and Bob, are all swimming happily around and have never shown any sign of illness whatsover since I added them to the pond last year.
Fish #3, I've concluded, is an accursed fish. That fish dies, I replace it with another, which subsequently dies as well. Today I netted out Fish #3 for the fourth time and gave him a hero's burial. (This involves flipping him into the bushes in a disgusted manner.)
It's always the new one that dies. I don't know if the others gang up on it or what, but I'm starting to wonder if there's some kind of plot to murder Fish #3 on a regular basis.
I'll bet Bob's behind it...
The good news is, I've decided to add another pond in the fall, so maybe I'll be able to have some new fish in THAT pond that Fish, Fish and Bob won't be able to get their evil little fins on. (Unless they figure out how to walk from one pond to the other.) I figure it's the only chance of survival for the new fish.
I also have a few residents that I didn't put in. They seem to have found the pond all by themselves.