I would have to agree with that. as far as i have ever researched, ophiactoids use their arms to filter particles from the water, or detritus off the sand/rocks, then use their little tube feet to transfer the particles to their mouths. i'm sure from time to time they would happen to come up with a small critter or two while feeding, but i couldnt imagine they would be quick enough to eat the whole population of pods.
what type of fish do you have?
often, when a population of something dies off, it is because it's food source has dwindled.