Is this Aptasia?

[Reesj]

I had this colony of brain coral for about 3 months now. I saw something small like this when I got it on its underside and I brushed them slowly.
It was on the sand bed but few days ago I mounted it in a rock. This is cause my damsels keep burying it in sand.

BTW it retracts completely when scared when fish comes and comes back out quickly afterwards.

 

[Phildago]

It doesn't look like aptasia to me...

Aptasia seen to have fewer tentacles that are longer.

 

[NielsC]

Looks like a little tubeworm to me completely harmless

 

[Vinman]

+1 tubeworm

 

[mta_morrow]

Tube worm or feather duster. Both a harmless filter feeders and great additions.