Larry hit it--Mangroves are nice, but not very useful for nutrient export because they grow slowly. I think they get mentioned often in the context of refugiums because it's just a nice place to put them--most people have hoods on their tanks.
Unlike algae, Mangroves are true plants (trees actually) and grow well in a sunny window or under 6500K light or warmer. "Algae"typically refers to aquatic, less advanced photosynthetic organisms.
Perhaps the best way to use mangroves is in a tank set up specifically for them--you can have a sand bed bottom, or even mud, and small fish.
The best