Most lr will do fine without a lot of light; depending on how much real sunlight gets let into the tank. Do you have an atinic or just reg light? The reason i am asking is you do want to promote coraline (pink) algea to grow on your rock. I have grown some of my own "live" rock and have saved myself bundles of money this way! Good luck! If you give us some more info like watts we might be able to give you some more advice! Keep us posted!