Not sure what these are. I apologize for the poor video but thats the best I can do. I put some frozen mysis in the tank and they came out of the substrate.
A piece of mysis touched the substrate and they came out of the sand and attacked it. Here is a picture. This is the best I can do :/ my illuminati zoas have been looking irritated the last couple of days. I did a dip and a few of those little critters fell of of them.
I can't see anything in that video. Now that said, the two creatures that emerge from the sand in my tank when food is about are Nassarius snails and Spaghetti/Hair worms. Look those up and see if that's what you're seeing.
I think you are right... The next feeding Ill capture one or two and take a better picture with the DSLR. I'll have to do some reading as when I googled them, several articles popped up from scholar.