i would back off the lights by 1 hour per week. if you are at 14 hours now ... back it down to 13 next week, 12 the next week and so on until you get it down to about 8 hours a day. you should then see the algea die off with a week or so after you get the lighting cut back to that level.
even my VHO's are not on that long. they stay on from 12pm through 8pm daily, with the PC's on from 10am through 10pm. they where on for 10 hours a day, but when i changed it, the algea started to disappear quickly !!