LR growth

[downunder]

What is the plant that is growing from my LR? It has large jagged leaves (kinda brownish). Looks like kelp, and seems to grow more horizontal than vertical. Seems to take over the rock. I want a natural look to the reef, so I have not done anything with it, but I don't want it to take over the rocks either.
Any ideas?

 

[fshhub]

sounds like it may be sargassum, which is a good thing, but unfortunately it only hangs around a couple of months in most tanks, normally about 6
i wish i could have kept it myself, it is attractive(IMO)

 

[lurch694u]

I had a alot of that macroalgae. Then I got a yellow tang and it was buffet time for him.. oh well