What kind of Macro?

I've set up a 150 gal tank with some fish, about 60 # live rock and 60# live sand in the lobby of my shop.
I have a 55 gal tank underneath that's divided into 3 sections. The main tank overflow drops into section 1 that also has a G2 skimmer. It flows over a wall into the center section and over another wall into the 3rd section that has two 800 GPH pumps. I have a couple of baffles to make sure the water flows throughout the center section and not just over the top.
The center section has a bunch of live sand and a little live rock from my old aquarium at home.
I want to grow a bunch of macro algae in this section to export nutrients. What should I get and where? Is this the right way to do this? Do I need anything else?

 

a common macro alge for a sump would be grape capulera it grows easily and fast. you might be able to get some from a lfs and on most sites under saltwater plants.

http://www.liveaquaria.com/product/scateg.cfm?pCatId=490

http://www.reeftopia.com/Marine_Plants17826.html

and other sites carry them as well

 

Chaetomorpha (spaghetti algae) and lettuce Ulva algae. The lettuce algae grows fast therefore removing excess nutrients rapidly and it can also be used as a food source. My tangs love it. Check out www.inlandaquatics.com
I bought mine a my LFS. Chaetomorpha is slower growing and both types do not go sexual and pollute your tank.