FAMOUS LAST WORDS OF MANY.
Get rid of it now. Trust me. This is why...and I had less than you...
Take the rock it is on out of the tank and kill the algae with peroxide and get every single strand. Mine started with 1 strand on a frag I thought was 'pretty'. Do not try to remove it while it is in the tank or it will spread. See above^. If it ever does get as bad as mine did or even worse, do not fret. I have been bryopsis free for a long time now. There are a few solutions.
Oh this sucks. That rock has corals growing on it.