What are these...? And there's bigger ones. I googled and found possibly spaghetti worms? There are 8-10 groups of these "tentacle things" the largest one has tentacles that move like worms but retract instantly when provoked. I was looking through the dark spots in my tank recently to see if I could get a better view of the big one that's when I noticed these guys. They lay "dormant" untill a light shines on them. Then these red "tentacles" come out and grab smaller items like algae and stuff. The largest one has green "tentacles" and has eaten a couple algae balls I had. The smaller ones have slowly moved towards holes and cracks. The largest in deep inside a live rock.