With no plants you won't be adding any ferts. The only nutrients that the algae can use will be the NO3 from the fish and the phosphates from the fish food. Test your nitrates often enough that you get an idea how fast it accumulates between WC's. If you want to keep NO3 at no more than 30 ppm for example. Figure out how many days it takes to get to 30ppm and that would be your WC frequency. Do a 50% WC, after 2 hrs take a NO3 test. This will be your starting point. Your Phosphates will be controlled by the regular WC's. I would not run your light more than 8 hrs a day. If algae shows up, lower it by 1 hour for a week and see if it starts to go away. But with that light, 7 or 8 hours will probably work. Hope this helps. Good luck. OS.