i had algae all over the tank just last week..... algae on the plants.. on the rocks... hair algea threading over just about anywhere, including the glass and even inside the filter medium....
my light was on about 15 hours a day........
End of last week, i decide on a complete black out over the weekend (saturday and sunday) and now, i just on my light for 1 hours in the morning (before i leave for work) and about 2 hours in at night before i sleep.
No signs of algae anywhere... i didn't even manually clea up those algae in the tank previously... they just dissappear on their own..... besides te black out and cutting down on the lights, i didn't do anythign else. feeding same about, no addition of new fishes also
so in a nutshell, i think 14 to 15 hours is too execessive.... hope this will help you as well