Baby snail? Slug? Friend or foe?

[PotatoPig]

So a few of these critters appeared on the glass today. I have (to my knowledge) Astraea, Trocus, Nassarius, and Nerite snails. Also (to my knowledge) one Bumblebee and one Stomatella snail.

In the sump I also have random tiny snails (round shell type, this isn’t one) and what appears to be one little Limpet about 1/4” across.

Any idea what these things are?

/apologies for the poor focus, my phone doesn’t recognize it as a thing.

 

[EeyoreIsMySpiritAnimal]

Limpet

 

[PotatoPig]

Limpet

Are these good, bad or neutral?

 

[EeyoreIsMySpiritAnimal]

Are these good, bad or neutral?

Good in my book.
Some people have reported a few varieties can munch on SPS but I've never had a problem with them.

 

[OrionN]

Poor focus so not 100 percent sure. If the foot completely covered by the cone shape shells then these are limpets. If the shell is kidney shape and foot extended be young the shell and they can be seen moving then they are Stomatella snails.
Both are great but Stomatella are better grazer IME.
If you get a few Stomatella snails in your tank and keep the water condition good and they have enough food they will start to reproduce.

 

[mww00ds]

Are these good, bad or neutral?

I love these guys. Got a couple that hitched in on my live rock when I first started my tank, and have done great at keeping algea down and reproduce on their own

 

[mww00ds]

wrong thread. LOL sorry

 

[ISpeakForTheSeas]

Good in my book.
Some people have reported a few varieties can munch on SPS but I've never had a problem with them.

Just to clarify this - there are multiple kinds of snails referred to as limpets:

True limpets are from the taxonomic subclass Patellogastropoda, and they're harmless/beneficial herbivores.

Keyhole limpets are fissurellid snails from the subclass Vetigastropoda; a handful of these snails from the taxonomic subfamilies Diodorinae and Emarginulinae are known to eat SPS:

t’s rare, but there are two taxonomic subfamilies of keyhole limpets (Diodorinae and Emarginulinae) that I have found research on showing that they have a handful of species in them that are either known to or thought to occasionally eat corals (I’d need to go digging through the papers again, but, IIRC, they only ate SPS , and they had pretty specific tastes/preferences).

just to reinforce, regular limpets are fine, and most keyhole limpets (including most from the subfamilies listed above) are reef safe; to the best of current scientific knowledge, only a very small number of them are not.

The good news is that most keyhole limpets are also harmless/beneficial herbivores, and telling keyhole limpets apart from normal limpets is generally pretty easy:

If it has a little "keyhole" or bullet hole looking hole on the back of it's shell (where the shell comes to a point) then it's a keyhole limpet.

true limpets (taxonomic subclass Patellogastropoda) don't have a hole on top of their shell at all, but keyhole limpets (taxonomic subclass Vetigastropoda, order Lepetellida, superfamily Fissurelloidea) all have one for respiration.

For some examples of true limpets:

Variegated Limpet

This is one of those spottings that made me smile, because this cluster of limpets looked like a town meeting, and it's something I'd never observed before. Cellana tramoserica, commonly known as

www.projectnoah.org

Limpets

Limpets

australian.museum

Patellogastropoda - Wikipedia

en.wikipedia.org

Some keyhole limpets to compare with the true limpets in the quote above: