Thanks I tried to suck one out of the sand but he hid under it fast is this a aptasia or a feather duster
Definitely kill it. Aiptasia X works great in these circumstances as they view it as food and they poison themselves from the inside out.
Guess I have always been lucky. Never had to deal with aptasia. I inspect as much as I can every piece of rock or anything that goes into my tank and check the tanks at the LFS before I buy.
Once though I had to throw away a small frag of coral I purchased because a sneaky aptasia was clinging onto it.
I had one that popped up on a Zoanthid Coral a few weeks after I bought it (thankfully my only experience with them), I identified it when it was very small and killed it with Aiptasia X and then popped off the Zoanthid Coral (it was dead by that point anyways) off of my live rock and threw it away nearly 2 years later and no aiptasia so I guess I got it in time.