I am betting that they were the red planaria from a frag from anathema? If so those are not coral eaters. Definitely not the same as aefw acro eating flat worms.
Okay too be more specific on the 100+ flat worms. It has been identified as Convolutrioba retrogemma. These flat worm actually keeps adequate light from reaching the coral in great numbers thereby "starving" the coral. It's believe that this flatworm also consumes the resident zooxanthella on the coral surface. In any case, it's a nightmare to see all these worms all over your prize corals.