I've had this frag in my tank for about 2 months and it has been doing well. Today I added some DT's Phytoplankton (first time I've added anything for inverts) as my gold Maxima was looking a little small. After I added a small amount of the stuff, this tentacle looking (translucent with a white tip) came out and started waving around. I know it is response to the DT's as it ballooned up (in a good way) along with all my other coral and clam. So what is this tentacle thingy? See pic ("tentacle" runs between the 2 red arrows).