Hi I wonder if anyone can help? I have a 230l planted tank. It is about 18 months old. I can't get on top of the green algae and diatoms and the plants just will not grow. I have tested all of the levels and they seem fine. I have two 59w, 93cm Superfish LED lights which are on for 7 hours a day which we have reduced from 8 hours a day. We feed with 1 capful of flourish iron and one capful of flourish excel twice a week. We change 20% of the water and clean the tank every week but the algae is back in a couple of days. The CO2 concentration is 28mg/l. Please can anyone advise?