Small small green and black tentacles on live rock...

Just thought I would see if anyone has any clue what I might be looking at. After I put some live rock into a small (25 gallon) tank there appeared on one of them a feather duster and this odd little fellow who has between 5-8 thin tentacles. (light greenish tentacles with intermittent black stripes.)

Its source (base) is hidden inside of the live rock. The thin spaghetti-like tentacles undulate frequently, stretching over the live rock.

It's pretty nifty looking - but small - and could be overlooked in a large reef tank (at least at it's present stage).

Does this sound familiar to anyone?

Many thanks.

Thanks for your response. You might be right. If it is a starfish - the tentacles appear very lengthy. After your suggestion I went and found this.

http://www.ucmp.berkeley.edu/echinodermata/ophiuroidea.html

....Ophiuroids are a large group (over 1600 species) of echinoderms that includes the brittle stars (Ophiurida) and basket stars (Euryalida). The more familiar Ophiurida, or brittle stars, usually have five arms and superficially resemble true starfish (Asteroidea). However, brittle stars have long, flexible arms (hence the other common name for ophiuroids, "snake stars" and a central, armored, disk-shaped body that is clearly demarcated from the arms. Instead of crawling on hundreds of tube feet like starfish, brittle stars move fairly rapidly by wriggling their arms. These agile arms are supported by an internal skeleton of calcium carbonate plates that superficially look like vertebrae, and that are in fact called vertebral ossicles. These are moved by a system of muscles and linked together by ball-and-socket joints. The body and arms are also protected by calcium carbonate plates, and the arms generally bear delicate spines...

It is amazing to consider that there are 1600 (+) known species out there. How many people have what I have versus what you have in your tank!

So is a starfish the only thing that might hide itself inside of the live rock and have this tentacle-esque things flittering about?

Cheers.

Ok. Another question related to the same fellow. A small blue-legged hermit crab who recently discarded his old small shell for a shiny new puka shell sauntered over to our recently confirmed starfish-- and I'm not certain...but he was either munching near the starfish or...!

So my question is - could a reef grazer such as this blue legged crab supplement his diet on occasion with starfish?

Cheers.