I was looking in my tank and I saw something that I had never seen before in my tank. it was like a snail without a shell or some kind of slug. It had kind of a round pulpy body and antennae and a mouth and moved like a snail. It looked like it was a purple/gray color with a white spot on its back.The only thing it had on its back was a small oval looking piece of what looked like a fragment/piece of shell. I'm wondering if its a bad thing or good thing to have and whether it could harm anything in my tank(toxic nudibranch).
thanks


I dont have a real camera so I tried to snap some quick cellphone pics.

alien....

Pretty sure it's a stomatella, but a better pic would help.

velvet nudi?

looked at it again and its definitely purple and on its back is a darker purple spot and in that dark spot is the hard white stuff. the white part is not round kind like a fragment piece.
could it be a snail growing a shell?? its still hanging out in the zoanthids doing stuff...

Difficult to identify from the photos.

But if the white part really looks like it's hard shell, then either Scutus or Stomatella snail.

Looks like a black stomatella

Figured out what it is.....

http://www.seaslugforum.net/factsheet.cfm?base=scutus

its a Scutus sp.: Limpet.