I've read this entire 67 page from beginning to end on my slow smart phone and have to say sushigirl is doing an awesome job. You have identified bristle worms, asterina stars, and flat worms more times than most would have the patience for. I believe I saw my creature twice. possibly in mr. Demeanor's post #380 on page 16, and definitely in wenwillwego's post #872 on page 35. You identified it as a peanut worm and mentioned you had never seen one with that type of markings. After studying the link on worms at chuck's addiction I still don't know any more than I've observed over several months.
This may be a type of peanut worm, but does not follow appropriate behavior for your everyday specimen. These ones sting, paralyze, and eat snails. I watched one nearly ingest a nassarius snail whole before bright light caused it to spit it out and retract. I also had cerith and astrea(spelling) snails that came with my CUC. Any snail that fell within reach never moved again. They loom in the darkness, mostly in substrate, but also in dark places on rock, and a few bold ones in the light. The tentacles flow in the current, but can also stretch pod and tentacles to reach for snails. I've tried to catch them and they are too fast darting under the sand. I've zapped them with aiptasia-x. They swell and seem to implode and disappear under the sand, but reappear unharmed a few days later.
Identification is only half of my request. Next comes the important stuff that really matters. So far they don't appear to bother coral(touching some micro zoas with minor irritation at most). They already ate all my snails, and generally stay hidden in the darkness. Are they a problem? If so how do I deal with them. Very soon I will be upgrading to a 56g column and really want to keep this very established and full of life rock, and just add dry rock for the bigger tank.
There are video's at
www.youtube.com/dbarter8872 and I'll also try to attach a pic, but I'm stuck on a phone without the luxury of a real computer. Sushigirl must be able to relate to how limited I am by only being able to use a phone. Thanks again and hopefully we can figure out exactly what these creatures are. I truly believe there's a little more to this than the simple answers I've got trying myself. Definitely not aiptasia, but I still seem to get that response a lot. The tentacles are way different. Any other information needed feel free to ask. I would kill(not really) to find out the exact name of these creatures so that I can research them thoroughly to decide if they stay or go, and how. Thanks again for all the great information and for your dedication to this thread and passion for this subject! That goes out to all the people on here trying to help you know who you are!
And please..... small words I'm still a noob and can be easily confused!