Green hairy algae.....how and why ?!?!

My lighting(T5HO) period is 8 AM to 8 PM......I don't use CO2.

I'll add ~12 amano and some duckweed soon !!!!

The tank is not near a window but I'll check for phosphates, that's prolly the problem....

Plants need phosphates so I wouldn't really be overly concerned about that. You do need a source of carbon with that much light. I'd strongly urge you to do DIY CO2 and/or Flourish Excel. I agree that you should reduce your photo period to 8-10 hrs.
 
Ok, I reduced the photoperiod to 8 hours a day(12 AM to 8 PM) !!!!

@ texasguy.....I'll try adding an hour or two of off time if it still comes back.....

@ tiki.....I know it doesn't foul the water but I don't like algae at all, one of them !!!
 
I have noticed lately in my tank that hairy algae has been growing where there isn't much of a current from my filter, I dont know if that has anything to do with it but it interested me, the way i have combated it is with a chinese algae eater they seem to have cleared a lot of it up over the past year. also i think it does come down to to much light, i often leave my light on for far longer then i should.
 
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