Kill the Fish?

Oh lord, this post is gonna make me seem like a nutjob....well, maybe I've already come across as one in my other postings, so what have I got to lose? LOL! Anyways, let me give you a little background info on the zombie fish that has come to live at our house.

My son has loved Elmo for a while, and Elmo owns a goldfish named Dorothy. Well, one day my husband and I went to PetCo and bought our son his very own fishbowl and a little fantailed, calico fish. Goldfish breed, but not gold, we just thought it looked cool. It has been with us for about 4 months now and for the past month has been acting very odd. Its fins are no longer fanned out, kinda skinny looking for lack of a better description, and it swims in a really weird and lopsided manner.

Oftentimes it just hangs out at the bottom pretty much motionles or hangs out at the top, motionless as well. We keep this little guy clean and fed, and our friends have the same type of fish in an even smaller bowl who is just flourishing. My whole thing is this.....it bothers me to see this poor thing act so sickly and look like it is about to shrivel up & die, but it keeps on hanging in there. My son keeps asking me what is wrong with it whenever it just lays at the bottom.....I don't know what to do? Help it "go to the light" and somehow euthanise it? Let nature take it's course? My husband laughs and says it is the zombie fish....and it really looks like the living dead. Kinda gives me the creeps actually. I should take a pic of it and post it on here.

And now to prepare for a barrage of animal rights activists posting and telling me I am cruel and unusual. I love animals of all kinds and would never hurt a fly....but this fish is just freaky.