The focal point of the picture looks to be some sort of rainbow monti (maybe a pokerstar, but the polyps on the top edge look a little bit orange...who knows)....
what he is talking about though is the tiny purple nub to the left of the monti.
As to value....I don't know....$10? Its pretty small. Deepwater type acros are pretty sensitive (susceptible to RB's and AEFW) and don't dip well. On the other hand that one looks like a very nice color; if you find someone who really likes the deepwater type then maybe it would bring more.
You could also make up some ludicrous name and "give" half to a high end store/hobbyist, then have them pretend to sell it to one of their friends for $400, then you could sell a frag for $250. lol.
If you grew it into a nice little golfball size then it should bring $40-50.
Hope that helps,
Ed