oh yeah, moonman makes good points. if you have no plants you dont need Any light LOL
I am also an advocate of java fern/ java moss. but You seemed pretty dead set against plants. But i have nearly always had very good results with these. NO extra light No extra fertilizer, No co2.I dont know how much difference a nice big java fern will make in your nutrient levels, but better than nothing. Plants Are the only other way to remove nutrients beside water changes.
I am also an advocate of java fern/ java moss. but You seemed pretty dead set against plants. But i have nearly always had very good results with these. NO extra light No extra fertilizer, No co2.I dont know how much difference a nice big java fern will make in your nutrient levels, but better than nothing. Plants Are the only other way to remove nutrients beside water changes.