They can. Some, I hear, are worse than others. Avoid the greens in particular; they seem to be the most predatory. Most won't hunt if they stay well-fed, though.
I have never noticed mine paying any attention to the fish. The only thing I ever see of it is ends of legs sticking out from rocks. Has never been all the way out since I put him in there.
Well mine or n others they come out at night I have vid of mine out at night dancing cross front of the tank .I had five chromis before I got the star fish.waited a year to get the star fish n now I am down two chromis . Seems like the chromis that I have left don't sleep n the rocks anymore. They sleep out bye front glass .i bought 3 brittle one definition star for clean up crew n tank . My tank is 150 gal tall . Reyes staying up at night see what's going on never see anything I like my chromis never had any problems till star fish.
Maybe it's just me, but that yellow looks like a pale green.
Maybe you need to start target-feeding it. I'm reading that they're more likely to hunt fish when they're not finding enough to simply scavenge, which makes perfect sense.
So I have spot feed my star since day one but I had heard about them hunting so in an experiment I fed the tank the same amount but did not put the stars food under his rock in 3 days he was out at night after his peppermint shrimp friend we had 4 and now we have 2 so I resumed spot feeding and no other corpses have been found
I have several in my 180g two are 5 years old about 24" in diameter they don't bother fish unless the give up the ghost...they do not go after live fish....great clean up crew