What is this branching white critter?

[MAH]

It hasn't moved in the past 12 hours.

 

[ISpeakForTheSeas]

It's a nudibranch of some variety (I struggle to ID the ones like this; I tend to do better with the bigger, more colorful ones). This one likely feeds on hyper-specific cnidarians (anemones, coral, etc.) similar to zoanthid-eating nudibranchs, monti-eating nudibranchs, etc.

 

[MAH]

It's currently in my refugium and it hasn't moved in 24 hours. There is another smaller once a couple inches away. So should I get rid of them? I know I had aiptasia in my refugium for the past 2 months and haven't seen any in the past 2 weeks since I removed 1.

 

[vetteguy53081]

It hasn't moved in the past 12 hours.

Montipora eating nudibranch - get rid of it

 

[MAH]

Ok, thanks. They are both gone.