snail-eating snails?

[Queens]

I have a couple of snails in my tank that were hitchhikers on my live rock. I've left them in assuming that they wouldn't be harmful. But now I'm starting to wonder -I found an empty astrea shell with a small hole, perfectly round, with perfect placement to suck out the meat.
I don't have a picture of these sanils, but they are dark grey, their shell shapes are similar to pasta shells, and they mainly stay on the live rock (I've never seen them on the glass), sometimes the sand, and they have a small tubeular nose, or mouth, or something that is always sticking out.

Anyone know anything about these guys?

Unfortunately, since I've set up my tank (about 10 months ago) I've experienced many snail deaths. I've found several empty snail shells over this time and am tired of spending a lot of money to replace them.
Now, there are some other hitchhikers that are probably not helping. I've taken out a large bristle worm/fireworm, (I didn't think that it was a problem until I saw it plow through some shrimp I set as bait). I also have many little hairy crabs with black tiped claws hiding in the LR. Including a fairly large one, that I'm now trying to trap (so far, unsuccessfully -the bait is gone but the trap isn't closed). This is definately a frustrating battle.

 

[romunov]

Many snails will eat other snails.

The Predatory Shelled Snails
Whelks

p.s.
Throwing out the bristle worm was probably a mistake. And now the good news - there's more in your tank. They're the ultimate clean up crew that eats uneaten food, diatoms, detritus, dead animals... you name it.

 

[Queens]

Thanks for the link to the web site. It sounds like it might be what I have in my tank. Still not sure though.

I've confirmed that what I took out was indeed a fireworm. It was huge. I couldn't find any thing that said they were benefitial, and I did find a post by someone saying that they'll eat all of your snails. It was cool at first, so I left it in since I don't have any corals, but it just got too big and fat for comfort.

 

[romunov]

You didn't search hard enough.

Polychaete worms

 

[Queens]

I guess what I had was the Hermodice Carunculata. Even though the article says to remove it, I guess it's mostly a threat to corals. It was getting big and fat off something though....

 

[romunov]

How can you be sure it was H. carunculata?
Did it move about during the day?

 

[The steven liu]

If you are lucky enough to actually have a conch then you can bet they'll eat all the mollusk in your tank. They are predatory snails who eat other snails but also eat table scratch on the substrate.