ID this little critter - good or evil?

[MRRBW]

I have spotted this slug like critter crawling on the back of my box filter today and another on my rockwork. Never seen them before and not if they should be siphoned out or let be. They glow this red/orange fluorescence under the led's which is kinda neat and they seem to move around like slugs and have their head stuck to the surface. Cleaning algae, I hope. Any thoughts and insights appreciated!

 

[MRRBW]

Only have an iphone, so the photos are not the best.

 

[jadwv2210]

The antennae make me think it's some kind of nudibranch. I honestly have no idea though lol. Maybe someone else can help more.

 

[Naiad]

Hard to tell from pics possible baby triopha maculata.

 

[Naiad]

It is a nudibranch. The orange makes me think a bryozoan eater. Where did they likely come from?

 

[MRRBW]

Hmm, thought it may be a nudi, but I have no idea how it would have gotten into my tank. Not sure what it's eating either, but there must be enough of it as there are at least 2 scurrying around. Always fascinated that after 10 years still seeing new stuff in the tank.