Aiptasia or something else?

Whilst giving my tank a thorough clean to try and eradicate some algae problems, I came across a strange looking creature. With 5 or 6 long tentacle like things, it looked like a cross between a star fish and a coral. It was a brownish/green colour and around 2-3 inches diameter.



I thought at first this may be an Aiptasia Anemone, however when I put my hand near it it disappeared (didn't see if it surried away, or burried itself in the sand). Can an Aiptasia Anemone move/hide or is this likely something else that I have as a hitchhiker? What else could it be?



Thanks