Critter id

[clhardy5]

I have several of these in various sizes on the plastic piece that flows into the media tray of my biocube. Is this some sort of snail baby? Or something else? Good or bad?

 

[JGT]

Limpet, herbivore, good guy.

 

[sfin52]

Agree a good guy.

 

[PghReef]

Looks to be some sort of limpet, a snail. Many are good, few are not so good. If you see them primarily on walls and rock work they're probably an algae grazer good guy. If you see them on a coral you got a bad one that eats coral.