Help identify this creature

[DocSmiley]

 

[DocSmiley]

Looks like some type of sea cucumber but it has thick armor-like scales. Found it in my tank with a flash light and I've definitely never seen it during the day. Im just wondering if it will mess with coral or not. I have had some mystery chunks taken out of my mushrooms. I just figured it was my lawnmower blenny taking a curious bite. Ive dealt with a lot of cucumbers but this thing seems much more ancient.

 

[DocSmiley]

I think I may have figured it out. A feather duster?