Some Kind Of Mollusc?

[ichy]

It's very small about 4mm and moves slowly.
This is the second time I've seen it moving on the rocks.
Is it a pest?

 

[ThePaliga]

I believe what you have there is a limpet snail. Used to have a boat load in my old tank. Although there are certain types that can be pests, that one right there looks like a harmless algae eater. Should multiply in the right conditions.

 

[SamB]

You must have brought it in on a frag or new live rock(?) and generally they are safe and beneficial filter feeders but I agree that you should keep your eye on it to determine if your corals are withdrawing

 

[Pistol]

Looks like a limpid snail, algae grazer, ok.
Check this site out http://www.lionfishlair.com/hitchhiker.shtml

 

[ichy]

Thanks everybody! I'm relieved to know its not a pest.
I was looking at the copepods crawling around the rocks when I noticed it.
Its amazing to see all sorts of things growing in our aquariums.
Just the other day, I saw a tiny purple sponge that looks like a heart with multiple aorta branches.

 

[ThePaliga]

This hobby is amazing for that.. I spend more time infront of a half empty aquarium than I do in front of the TV