Nudibranch or something more nefarious

[Sarah Grace]

I just found these little guys all over my refugium, hoping someone can let me know what they are and if i should start removing them. Thanks ;)

 

[Lionfish Lair]

That's a good flatworm! I like to call these "Ghost Flatworms" and are not a risk to your tank at all. Their numbers don't climb out of control and they don't use your light as energy. They are awesome and usually only do well when you have a great copepod population going on. If your population drops, they will die off.