Fast moving, live rock bleaching... sea slug?

[pringlescan]

I've had my tank up for about 3 months (FOLR) 75g.

I thought I saw a snail cleaning my rocks. I'd notice him at night but he'd quickly disappear within a few seconds of turning on the light. Everyday when I woke up a section of the rock would be picked clean.

I finally got a good look at him and he's big and doesn't have a shell. The size of a frito but bigger. I see some sea slugs in photos, but they're all colorful and this one was more tan/brown like a land slug.

:confused: What is this thing? Will my live rock grow it's algae back? Is he bad?

I'll try to get photos but he's very elusive.

[phenom5]

stomatella snail? That'd be my guess...without a picture.

[MysteryReef]

I had a couple of ugly tan to brownish slug looking things that came in on LR in my 150. They never hurt anything and they would also clean patches of rock, small patches. They never put a dent in any corraline algae...they would however strip the rock of any "short fuzzy soft algae".....

If this is the algae that they are eating, why would you want it to grow back? The two I had also were quite elusive when the lights were on. Occasionally I would get to view them during the day on the glass. The 150 is gone now, but I believe I cam to the conclusion it was a small sea cucumber of some type.

Id is flesh smooth or bumpy?

[pringlescan]

The creature was smooth but had a single nub in the center. I didn't notice any feelers towards the front but it really does move surprisingly fast. Due to the lack of contrast he's hard to notice/get a photo of.

It was fine when he was cleaning the nuisance algae, but now the rocks look like dry rock rather than live rock, it's completely stripping the color, which for me is undesirable.

[Sk8r]

At 'the size of a frito' it's not a stomatella, which are more dime-sized. But it might be a chiton, which has a mantle that comes up over its body except a bit in the center of its shell. Chitons are nocturnal, or at least don't like the light, and are several dollars worth of critter if you buy one. Cowries also have that shell-covering mantle, and are a type of snail. In either case, good find. If it's something other, as long as it isn't eating your coral or fish, it's ok. Coralline is expendable, believe me. It grows back. Fast.

[pringlescan]

I managed to get photos of a smaller slug like creature in my tank. I don't think that he's the speed demon that I originally posted about. Any ideas?

Album of photos:
http://imgur.com/a/rMeUn

http://i.imgur.com/P8QL23q.jpg

[cloak]

Stomatella snail.