Identfy Feathery Slug

[4lti7ude]

Hello again.
I recently had to switch my tank to a 20Gallon tall since the 10Gallon was leaking.

A few hours after the lights had been out and all the fish were settled, I saw the nudibranch again!

But I was reading up on nudibranchs lately and im kinda scared it might be a bad one.

http://www.peteducation.com/article....+2167&aid=3354

"A more recent nudibranch pest that affects SPS coral aquariums has recently become prevalent, and prefers to consume corals of the genus Montipora and Anacropora. These nudibranch are very small, attaining a maximum size only up to half of a centimeter, are pale white to tan in color, and have many branch-like appendages along their back. They are very damaging pests in a reef aquarium that can multiply and consume corals in a very short period of time."

Every time ive seen this I havent had a regular light so I can just see it with the moon light. I dont know the exact color but that sounds like him...

Any idea what I should do?

The only thing in my tank that I think would be eatable are my frogspawn and 2 mushrooms.
They both arnt damaged at all tho...