Hmmm, horror stories I've heard ... let's see...
I knew one carpet that took down a yellow tang, and there's an LFS by me that was losing percula clowns to the carpet in their tank about a year ago. It took a while for them to clue in, they told me ... but they eventually caught on when day after day there were fewer fish in the tank ... and sales wasn't the explanation.
I had a friend who, years ago when he had a reef, had a carpet in with his ribbon eels and he told me it caught a ribbon once, and there was absolute pandemonium, mayhem and carnage in his tank as the eel wrestled itself free. Both carpet and eel lived to see another day .... but the tank was a mess.
I myself have a carpet. I wouldn't go so far as to say it's ever wiped out all its tankmakes ... but it certainly is a ferocious eater. And once it's caught something, that's it. I've even lost snails to it. It's never taken the one hermit crab in it's tank .... although I've even heard of hermits meeting their fate in a carpet. I've never had fish in with it, so I can't say I've ever "lost" a fish to it ... but the reason I don't have fish in with it is due to that there is no doubt whatsover in my mind that most things (if not all) would be goners sooner or later. (My carpet tank is a fairly small tank and it is a dedicated species tank for the anemone.)
I feed my carpet fish ... I used to feed it shrimp and other things but all it ever eats now is fish. I feed mine silvesides sometimes, but mostly I chop up some cod or snapper or other fish that I bought at the supermarket and feed it a good 1" or 2" square piece of fish every 2-3 days. If I don't feed it that often it gets cranky on me, toppling rocks or going for a wander.
Perhaps in a larger tank the risk is minimized but in my opinion any fish that is a bottom dweller or percher, or just a dumb blunderer, is very much at risk no matter what you do.
These are all based on S. haddoni. I don't know what it's like with S. gigantea or S. mertensii.
