sorry the response took so long...it doesnt really simulate the sun like i thought it would...it basically just moves it back and forth across the rail, which helps get the light to all crevices, not just whatever happens to be under it...so say for sps, when they get large and start bleeching on the bottom because of lack of light...this light will help get down there...its more used in horticulture making sure those plants get tons of light everywhere...but i think its cool, and can help me use less light...where i'd normally use three, i can do 2 and use supplement on the sides to keep it lit everywhere.