through my experience with FW and SW tanks, all fish will react different towards tank mates
I have a small scorpian in one of my tanks, he's a carnivore, sits around and wait for other fish and iverts to come by so that he can pounce on them
I have a damsel, some crabs and a nudibranch in there with him, he only pounces on flakes, but he let's everyone else know who's boss
and my fw, my oscars eat goldfish feeders from time to time, except this one gold fish, they won't eat him, became a tank mate and out grew the oscars
I want a puffer, but my lady won't let me have on right now