It's dead, Jim.

[pseudorand]

So I'm looking at my tank and all of the sudden this thing floats down by one of my clams. No, not the crab molt, the white harry thing.

My best guess is a hitchhiker I didn't know about, but I'm desperately searching my tank for anything missing. It could be a rock nem if the loose color when they die. It does appear to have a foot, so anemone fits. The fish don't seem interested in it, so it's not tasty.

And if it was good, where do I get another one?

 

[pseudorand]

I may have answered my own question. Astrea snail. Now, what would make it die? Plenty of algae, so it could've starved. Perhaps the crab killed it and molted as a result of his fat tummy. I suppose I should do a water test (looked good last week), but I expect I need an extended one to look for astrea-killing stuff. Anything specific to look for other than copper (which we can't test for at low levels in salt)?

 

[Zoa_Fanatic]

I may have answered my own question. Astrea snail. Now, what would make it die? Plenty of algae, so it could've starved. Perhaps the crab killed it and molted as a result of his fat tummy. I suppose I should do a water test (looked good last week), but I expect I need an extended one to look for astrea-killing stuff. Anything specific to look for other than copper (which we can't test for at low levels in salt)?

Astrea snails can’t flip themselves over. Likely fell and died and a crab ate it. Or it fell and couldn’t defend itself and a crab ate it. Switch to banded trochus or cerith snails. The first can flip itself the second can defend itself with its door.

 

[Little c big D]

I think it's likley to have fallen. It's happened to me with the turbos.

 

[Sharkbait19]

How long ago did you get it? It’s also possible it just never acclimated well. Happened to a few of mine when I got them.
Or it got flipped and was good invert food.
Hermits love the dead snail, but it also is an ammonia factory so best to remove.

 

[Zoa_Fanatic]

I wouldn’t worry about your water. Snails are cheap and they die, a lot. Astreas aren’t a super long lived species anyway (that being said I have one going on 6 years old).