Tropical Fish Keeping - Aquarium fish care and resources - ID strange white nudibranch-like invertebrate

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ID strange white nudibranch-like invertebrate

I've had my 44gal tank running for about a month now, put in live rock which were infested with some isopods and diatoms.
I was trying to capture some isopods I thought were Cirolanids, so I put the tank in total darkness for a few hours along with a trap. When I removed the trap and turned the lights on, there were several of these strange twin-tailed invertebrates apparently cleaning the glass. Pictures below
http://www.fishforum.com/userpix/6841_100_2398_1.jpg
http://www.fishforum.com/userpix/6841_100_2401_1.jpg
http://www.fishforum.com/userpix/6841_100_2402_1.jpg

Looks like it may be Amphiscolops sp., They are reportedly harmless.