Can a large nassarius snail kill a small fish?

Can a large nassarius snail kill a small fish? I have a large nassarius snail. 3"s+ including the foot. I have had two fish go missing and a new occurrence with a third.

So the first two fish I just chalked them up to dying in the rock and being eaten. This new one though is a bit different. So I added a firefish to my tank and it immediately went into hiding. I was home for about 6 more hours and didn't see it. I went away from home and monitored my tank via webcam. I saw the firefish appear on camera about 24 hours later and it was swimming strangely. At first on its side, then normally, then inverted in the corner. 3 hours later it was on the sand appearing to be dead and the nassarius snail approached and began eating it.

Is it possible that while the firefish was sleeping and hiding in the rocks near the sand that the nassarius snail attacked it and it eventually died?

I wish I could get a pic of the snail but he rarely comes out. He is likely very full now from eating most of the firefish and I won't be able to coax him out for at least a few days. I would like to put a piece of frozen fish or shrimp on the bottom to see if he will come out. His siphon is black if that helps.

This picture is of a shell from another nassarius snail I bought at the same time which died. The snail has since grown quite a bit. This should give you an idea of the size of the snail.

Thanks
 

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Where did you buy the Nassarius from? I've never (been in the hobby since the 1980s) seen one get 3". A couple of things come to mind.

1 - If it truly is a species of Nassarius, it *likely* didn't kill the fish, but it definitely would eat dead fish.

2 - How long has your tank been setup and what are the water parameters? I'm wondering if there's something else at play here?
 
Getting him to come out so I can remove him may take time. I can't believe a so-called reputable place would have sent me a welk and not a nassarius snail. I won't use them again. I will update when I catch it.
 
Yes, I would like to see a picture. That said, how big was the snail when you got it? If it was smaller, depending on shell shape, it could have been mistaken for a Nassarius.
 
Well this is interesting. I'm surprised I don't remember this discussion from when it happened. From the thread posted by @pagojoe in response to someone sighting Dr. Shimek as stating, "Nassarius are whelks that have gut and behavioral specializations that seem to prevent them from attacking live prey. They, however, have many near relatives that are not as "fastidious."

pagojoe's response:
Dr. Shimek's excellent work on Nassarius involved Atlantic species, and as far as I know never included the Indo-Pacific species that are repeatedly implicated in the deaths of aquarium animals. The species that are most often accused of killing snails, clams, and other animals are the ones sold as "Giant Tongan Nassarius," usually Nassarius arcularius and Nassarius coronatus, although a couple other species may be sold under that name. The sellers typcially identify their large snails as Nassarius distortus, which they usually aren't. Interestingly enough, the snails pictured in the marinedepot thread referenced above are the true Nassarius distortus. Thus, there are apparently at least three species of Nassarius with questionable feeding habits. "Obligate scavenger" sounds like a name you'd call something that you wanted to BELIEVE wouldn't kill anything else in your tank. If I were an obligate cannibal, and could readily eat you if someone bonked you on the head and killed you, I'm no less well equipped to eat you if you are still alive. In fact, I might not even be able to tell the difference: if these snails can eat a clam or sea hare when they are "sick" or "dying" they can certainly do the same to a healthy animal that is in a vulnerable position (i.e., where they can't close, or hide, or burrow, or climb, or whatever). I doubt they check pulses to see if an animal is dead before they eat them.

It doesn't surprise me at all that your Nassarius might go after a soft-bodied animal like a sea hare.

Cheers,
Don
 
Some other clues that might help you ID it. Does it's trunk have a pattern on it or is it solid black? Whelks supposedly have a "tattooed" trunk. Also whelks apparently don't really dig in the sand. Nassarius are pretty much always buried until night or feeding time.

Whelk versus Nassarius | Melev's Reef
 
I am going to try to get him to come out tonight. I have a small piece of fish being held down by a rock on the sand bed right now but no activity. Hopefully an hour after the lights start to go down he will come out so I can catch him.
 
Things are much different tonight. I came out to get a glass of water and they were having a party. They were all out running around. They would normally be hiding which I thought was normal. The pics I took are too large to upload I guess.,
 
I resized the pics. As you can see they are all out and about and have no fear now that the welk is gone. They must have known as soon as I removed it that it was ok to come out and not be afraid. That peppermint shrimp has never come out like that. So cool. Excuse the tank. I am fragging some things right now and it isn't much for a display tank.
 

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