Strange slug beasts

Ok, I know everyone wants pics of this, and I wish my camera was good enough to take them. But everytime I take it, the buggers blend into the rock.
They are about an inch long and speckled. I thought they were snails without the shells, but they are fast! Much faster than a snail. I haven't seen any damage to my coral, but I am a bit nervous. For those of you that are familiar with freshwater fish, it kinda reminds me of a freshwater flounder. Speckled like that, but they don't swim.
Should I be nervous?

Clay

 

Maybe stomatella, they are fast and look like slugs, but they have a small shell. Could be a nudibranch as well, but its hard to say without a pic, try going here for an ID:

Melev's Reef - Visual Identification

 

I am going to say stomatellas as well. Harmless algae grazers

 

cement skis, thank you for that link. i clicked on it at work, and almost went into convulsions. beautiful.

clay

 

There's lots of good stuff there, especially if you are trying to design a sump!

 

thank you both for the answers. that was kinda scaring me, since i have put the time and money into this project. but they were very interesting to watch.

clay

 

it is either that or the keyhole limpet. heck, i may have both. have about 3-4 of them. are keyholes herbivorous too?