there is some red version of grape calerpa, and my LFS has some red
"stuff" in his macro algae tank, that looks to be caulerpa, but im not
sure what species. but definetely sounds like hair algae to me too, i
have not had a single case of red hair algae that i can recall in my
time. must have been a culture that got into your tank from a live
rock or something that had a bit of ammonia, or nitrites to feed on
while the tank was cycling before other bacteria or organisms had a
chance to keep it at bay. or im guessing possibly your light, Peter
Pan, could possibly going off spectrum? are you running NO's?