I think you need way more lighting. if you get the plants growing well you wont have to worry about algae because the plants will use up the nutrients. i dont think the 4 hour plus 2 hour break on the lighting is a good idea. it doesnt sound very natural. i think it would probably be better doing 8 hours in one go.
i have a 250l planted tank with 108w fluros running 12 hrs and i dose with PMDD every few days, and im throwing out clippings every week. not a spot of algae growing!