That looks like some kind of a nudi, but its really hard to ID from that picture. I would suggest taking a better picture and getting it ID'd before adding corals.
I picked up some Zoa's from a reputable dealer and did the dip the coral procedure and all, however it had some zoa's nudibranches which really upset my other colonies. I did not notice at first however one day I found larvae on the stems of the zoas which made them close up. I had to pick them up with my wife's tweezers (don't tell her that) and it took about a month to get rid of all the nudis and the eggs they laid... (collected about 15 nudis, maybe more and 30+ eggs)
A few months later all my zoas have came back to life growing happily except one frag (which also happened to be the nicest looking frag). I think I'm going to try to give it a revive dip and look closely to see if there is anything else bugging it (have to be really patient and careful as these nudis take the color of the plant.. I did use a magnifying glass and I have good vision)
Also I know some are against FW dips, but in my experience, I found that the corals survive but all the pests dont do well in FW dips, especially flatworms and nudibranches along with other small critters. For dips, I use Two Little Fishies Revive and in all honesty, I cant say I'm sold on the product.
