Can't tell you how much but not too much and run less hrs for new tank, like 6? You dont need much light if you have anubias and moss only. I run 60w cfl using the stock clip light on my finnex 4g, I guess 2 inches above tank, everything is ok, pumping 1bps on a gla atomizer, fish and plants are happy. Monitor and adjust. Play with it, thats how you learn.