ID help please

[Bojangles]

This post is more for the expert opinion than an real exact ID. I had gotten a piece of rock that had 2 orangish/brown critters in it. THey look like snails if a snail didn't have a shell. I've had them in the tank for about 3 months now and they've grown from pin-head to about 3/4 inch. Now they are alittle bigger I've noticed that they are:
nocturnal, they have 2 eyes, 2 antannae and they eat algae by the same "looking" mouth as a snail. They are very fast and I've never seen them not on the glass moving around.

I'm not worried about them as much as I am curious.

Thanks to anyone that replies.

 

[Anonymous]

Without a pic it's impossible to say for your sure but my guess would be a Trochoidean gastropod probably Stomatella varia.

Here's a link on snails that also describes these:

http://www.reefkeeping.com/issues/2004-05/rs/

Regards,
David Mohr