Suddenly, Aptaisia?

I have an odd question.  I have a bio cube 8 with one 20 lbs piece of live rock in it.  I put that chunk of rock in about 3 months ago now, and the tank is getting into a good balance.  Almost all of my cyano algae is gone, I'm getting good coraline algae starting to develop, a bunch of little snails and feather dusters and 'pods and the like.  So, anyway, I sat down and stared at the tank for a while today, and I noticed one very small aptasia looking thing.  I had seen No aptasia in the tank ever, and this one is tiny.  So my question is, is there anything that looks similar to aptasia but isn't it?  This one doesn't look exactly like what I've seen around.  Not much of a trunk, just a bunch of little tentecles.  Also, if it is aptasia, why did it 'show up' now, 3 months down the line?  I was able to rid it from one of my other tanks, but if it is something else, I'd rather it sticks around.  I like all the little creepy crawlers.
Thanks,
Michael