yeah if the fish are even close to being able to fit in their mouth then they may become dinner when the lights go out, even if they cant straight up swallow them i have seen them twist and jerk till they cut a fish in half, i threw in some dempsey juvies one time for food and my del grabbed one twice the width of his head and was swimming around with it until he finally got it small enough to swallow, but then he leaves a tiny severum juvie alone that he could easily swallow, so i guess you never know haha