How old is the tank? Probably some sort of Pod, Just means your tank is maturing. check this page out and see if it's any of these.
Pods | Melev's Reef
Spiny worm might be a bristle worm, its harmless if so. Actually it's a beneficial addition to your CUC. Not pretty though, good thing it comes out when the light are off. check here for possible ID's
Worms/Starfish/Cucs | Melev's Reef