Snail ID?

[BirdGuy21]

Found this guy hanging out on my filter sock this morning. Looks like a small snail. Has a hard shell that has a spiral in it, but when viewed from the side the shell is mostly flat and just rests on the back of whatever this is.

 

[reef lover]

Collinista snail good guy.

 

[BirdGuy21]

Good to know. Wondering how it got in. I’ve added some corals lately but dipped them with s bayer mix. The GSP was attached to a tiny piece of rock, so maybe it hid out there.