Maco killing machine....

[Matt]

Well, that picture is blurry, but I think your description pretty much makes that stuff out to be "feather caulerpa" -- it is a pretty common macro algae, but you don't want it in your reef.

Picking it off by hand is the best option from my experience. Take the rock out, and put it in a basin of SW, and with tweezers... drive yourself nuts. Repeat as necessary every 4-6 weeks.

Some tangs and butterflies are known to occcasionally eat it, but nothing nano-friendly, AFAIK.