Yes, that is them. I have removed approximately (No kidding here) over 200 in the last 4 days and would guess there are another 2-300 still in the tank.
I purchased a product similar (would assume) to Joes Juice, which smells like lime juice but it does not actualy kill them just makes them kind of wither for awhile and sometimes makes them weak enough to come off the rock using a siphon.
Yesterday I used a smaller hose and as I ripped them apart/off with the knife held the siphon close to suck up all the little parts and their bodies.
So, guessing the nudibrach mentioned in the link will not eat them nor will peppermint shrimp.
Need to do a search, want to feed them to something.
This all started when two came in on a rock with a coral and I thought "They are kind of cute, why kill them"....Oh man to have that day back.