Cool!
I was told by some divers down in Key Largo that when they are running quality tests on the local reefs and they see living sea spiders in sampes they know that things are good. They said sea spiders require extra pristine conditions to thrive.
They are really interesting but I think they can be nuisance to corals.
We had a zoa eating spider a few years ago. Was a crazy looking little guy. Wife saw it on a zoa colony that had been losing polps quickly. Coral rx dip did the trick.
I just did some rock rearranging yesterday along with some hair algae removal that became a problem but is taken care of now, and as I was taking a rock out I saw one of those fall out and at first I thought it was just some type of brittle star, but after seeing your picture it was exactly the same, so whats the consensus are they good or bad?
LOL! Just found one of these guys the other day as well. Luckily not in any of my tanks. I did a freshwater dip and it looked like it was still hanging on so I did a iodine dip in saltwater and it was still hanging on. But then I started to think and basted it with a turkey baster and off he went floating dead. So I'm not sure if it was the freshwater or iodine dip that was able to kill it but at least I know that one of the two does the trick!