Nudibranch? Stay or nay?

[Aurortpa]

Found this guy scooting along the glass. Tank is only 5 days old, cycling with 20# liverock (JBJ 28 professional LED). No corals in the tank, there seem to be the slightest remnants of sponge or soft coral that matched the yellow on his tentacles...but not definitive. Any clue if he's ok to stay? I probably won't add coral for months. He's probably just under a quarter of an inch.

 

[Sugar Magnolia]

It's a coral eater, aeolid nudibranch.

 

[jraker]

yeah, if the color of the nudibranch matches any coral, it is probably predatory on that coral