Starfish identification help

[scase]

I have had this small white starfish in my aquarium for quite a while. I believe it probably came in with some live rock. When my son first noticed it, the starfish was about 1/8" in diameter and it's now about 3/4". I hope the image came out with good enough resolution for someone to (hopefully) identify it.
Thanks,
Sean

 

[JohnK]

It's probably an astrenia, though it looks slightly atypical in the pic. Astrenias are quite common in reef tanks. They will reproduce by dropping arms. You'll probably have many in a surprisingly short time.

There are occasional reports that some types of them may be predetors, but I've never had a problem with them, and most people have them in their tanks so I'd say don't worry at all.

 

[APISTOBORELLI]

The arms look round. That might not be an asternia.

 

[scase]

We've had it for about a year now, no more have appeared, it hasn't dropped any arms yet and has always been very even and symmetrical in it's growth. Also, even though it's hard to tell from the picture, it's actually a fairly bright shade of white. Hope this helps some more.

 

[APISTOBORELLI]

Does it move in the sand at all? Maybe a sifter.

 

[scase]

I thought that might be a possibility. It's usually out of sight, it could be in the sand, but I haven't seen it in there.