This has been growing on some new live rock that I got about 2 months ago. Its took it about that long to get this size. Just couldnt find anything that looked like it. Also should it stay or go?
I had the same thing when I first started my tank. It disappeared after a couple of months. Didn't seem to do any harm. Probably fed some of the tank residents.
I would guess Sargassum . Also known as Gulf weed or Sargassum weed. Assume in a fuge, but not normally eatten by most of the critters kept in a reef tank.
Rich