Any idea what's on my inverts?

[tfrey]

Hi, I'm fairly new to this hobby but so far am quite addicted. I'm working on a reef tank and have noticed that almost all of my shelled invertebrates are developing small white spots on their shells. It almost appears like a calcium build-up. I've tested my calcium and have just not got it to around 400.
I'm going to attempt to post a picture in hopes that somebody else might have some ideas on its identity. Thanks in advance!

Tim

[OrionGirl]

Stony tube worm shells. Very common, harmless. If you look closely at the opening, you may be able to see a tiny pink-ish tuft--like a tiny feather duster--that's the feeding crown of the worm. They tend to settle on everything, but are very noticable on shells and the glass.

[Liquidcfour]

just outta ceriosity?
are they generaly a good sign? or a bad sign?

thanks,
brandon

[OrionGirl]

I'd say good, simply because they aren't bad. They are a sign that your tank supports micro crustaceans, like pods, but it's not like they are a huge benefit to the tank either--just simple filter feeders.