I recall years ago when I worked at a reef LFS I came across a very large trachyphyllia in a display tank consuming a fish (a 3" sleeper goby if I remember correctly or something similar), it had swallowed three-forths of it. Not sure if it captured it alive or not, but these large LPS corals are quite capable of eating large food items such as whole silversides.
In my reef tank I have a trachyphyllia that probably has the potential of eating my fish (I have a pair of azure damsels and a royal gramma) but the fish are quite keen at disappearing when the lights go out (which is usually when the open brain coral extends its feeder tentacles).
I have a orange-ball pseudocorynactis (a very anemone-like non-photosynthetic corallimorph, or member of the mushroom coral family) that is extremely predatory in nature. It seized and consumed several fish, invertebrates (such as sea urchins, crabs and large snails) and demolished corals before it was given to me. Since acquiring it, I've kept it in a solitary set up.
African cichlid and saltwater aquariums