The pic you posted looks like a paly was trying to eat a floating zoa. I had to look at the pic for awhile to determine this. At first glance it looked like a piece of prawn or a worm but after closer inspection it definitely is a closed up zoa, look at the opposite end of the palys mouth and you will see a round knob with stripes, in the orifice a few green frills.... Cheers!
Didn't even read your title, you should change it to Apex predator paly eaten Zoas!
Sorry too much shark week....
