Hey Denise,
it's mainly forms of algae that your talking about I think. All corals soft or hard are living animals as opposed to plants. Algae in the marine aquarium is quite a bit different from the algae in freshwater. One major difference is that we Want certain types of algae in the marine system! Most marine algae is plant like in appearance. The algae that has the largest circulation is Calurpa, and will grow very well in medium lighting. One benefit of growing calurpa is that it will use nitrates as a food source. The hobby has pretty much decided that it is effective enough that you can grow it in a sump style filter, without skimming and achieve optimum conditions as never seen before. As a reference you can check out the Ecosystem brand, they are debatably the current leader in this method. Whether you go as far as using it as your primary filtration or just want to keep some in the tank for added color, as well as a little benefit via nitrate consumption and fish food, it is easily done. The typical problem in the latter is getting enough in there to outcompete the fish consumption. It will do well in medium light, and of course, do even better in strong lighting. hope that helped some...Dave