I had some show up in my 40 reef. I tried fighting them off for awhile with joe's juice. Just when I thought I'd have the upper hand, bam they show up again. So I hit the 10 that I could see and I bought 2 peppermint shrimp and I haven't seen any pop back up. It's been about 6 months now, so knock on wood, I think I got it.. good luck oh and about getting those nudibranchs(sp) once they eat all the aptasia, they will starve.