I'm not sure what you mean, if you are referring to sessile inverts...they aren't plants, they are animals, some with photosynthetic algae contained in their tissue in a symbiotic relationship. If you mean macro algaes...yes.
If you simply want to cut down the cost, use less LR
and more base rock. I do not think it would look as good without the rock and I have serious doubts as to how feasible it would be to try and keep sessile inverts without LR
and/or base rock.