You're running an IM 40? For a sumped setup, sure, consider a refugium. For an all-in-one tank, it's way more trouble than it's worth. Get one of their mini-max reactors and throw some GFO in it, don't look back.
Nope. Corals are the best for sequestering and esporting nutrients. (And just FYI the terms LPS and SPS have no relavance to a corals husbandry requirements.) This system was set up with a refugium and calurpa racemosa. Initially there was good growth with the calurpa but after a year and half it stopped growing and slowly receded as the corals took over:
GRJ 500 http://youtu.be/_Uf5IyXvajg
Green Slimer Timeline https://www.youtube.com/watch?v=DyM6Y39iQ8M
And some algae can be detrimental for corals:
And you might find my thread here interesting: