Cut your lighting down to 6 hours only until the diatoms go away. Ten hours is way to long to have your lights on. Also if your getting direct sunlight in the tank, not indirect light from a window, then put a piece of cardboard or something over that area of the glass again until the diatoms go away. It may not look pretty but for now you need to block it off. Later on once the tank is balanced you can remove it as contrary to popular belief direct sunlight in a tank does not automatically mean your going to have algae issues. Two of my tanks, a 20L and a 220g, get a lot of direct sun daily for 2-4 hours depending on the time of year and where the sun is in the sky.