Can anyone ID this? (Think it might be a plant)

[Rannoch]

This plant/coral came with my muchroom corals. Never saw it when I purchased it and after a few weeks it started growing. Now it is really big after a few months and I have yet to find anything on the internet to ID it.

Picture:

Close up:

It is kinda like purple lettuce. It doesn't seem to react to light like the muschroom corals. (IE. It does not shrivel up when the lights go out).

Any info would be greatly appreciated.

Thanks

 

[Hormigaquatica]

It is an algae, rather than a coral. I would post this one in the plant/macro algae forum for a better ID, but if I were to venture a guess I'd say Halymenia. As you've noticed, it's a very fast growing algae, great for soaking up nitrate and phosphate, and is frequently used in display refugiums.