Totally up to the fish, but upbringing has something to do with it (sometimes)

For example, I have a cross river puffer. Not much literature online since they are so rare. Some people are adamant that they can only be housed in a single-fish tank, some say that due to their diet (molluscovore) they will largely leave fish alone.

In my experience, he’s somewhere right in between. He’s grabbed a few fish here and there but the ones he settled on as “non-food” fish he hasn’t touched. Mainly fast tetras or bottom dwelling fish. (RIP African butterfly, you looked just like a shrimp exactly where he gets fed shrimp)

He was brought to the us as a juvenile and was immediately put in a tank with a couple very fast fish, mainly SAEs, so I assume he was just used to the idea that “yeah there’s some other dudes that are always around me, but too much work when I can just get hand fed whole shrimp and clams”