A few (or more) years ago, I came across a baby electric cat in a department store pet department. It was about 1.5-2", and when I asked about it, the female employee looked at the listing written on the tank, and told me it was a plecostomous.

Admittedly, there was no electric cat listed, which was why I was asking to begin with, but I figured it was a bargain at that price, so I took it home. Placed in a 55 gallon african (the c-word) community tank, by the next morning it had killed one fish, a second was almost dead, and a third was never quite right after.

So much for my theory that being small, it would learn to get along with others

I moved it to a 20 long by itself, and got curious one day about how much shock a small fish like that would actually produce. The result was mild, a fresh 9-volt battery on the tongue feels more painful than the shock from the little guy. It grew, and at about 3", I gave it to a friend who had a 125 housing three full grown oscars and a pacu the size of a dinner plate. The first oscar saw the little fish, and thought "food"

It got close, then suddenly turned away, twice. The second oscar only needed to learn the lesson once, and the third didn't act interested at all. The pacu, which also ate feeder goldfish just like the oscars, seemed terrified from the start. A couple days later, it was funny to watch. All those big fish, afraid of such a small fish, and constantly keeping as far away from it as the tank would allow. If the cat went from the left side to the right, the others went the opposite way, like they were attached by an invisible bar. Makes me wonder what, if anything, preys on them in their own environment.