Haha well, there are a LOT of species of nudibranch. Check out this list and see if you spot yours: http://www.seaslugforum.net/specieslist.htm@dr_schell, you may be able to tell me off the top of your head whether the nudibranch is a good or bad citizen of the reef. Mostly black with a white/yelling outline on it's frill. I'll try to get a picture if I can find it again.