Green Algea - please help

[tank202094]

My tank 75Gal is full of coraline purple algea on rock and around tank, and some on sand. All of sudden I saw the sand and front glass starts to have green algae instead of purple. Does anyone know why? Is it because my light bulb are old?

I have Nova Extreme 48" T5 4X54W (2 actinic and 2 daylight, moonlight) that I turn on for 10hrs on all 4 bulbs a day.

 

[afboundguy]

How old is the tank, what are you ammonia, nitrite, nitrate and phosphates at? Are you using RO/DI? How old are the bulbs? When bulbs get older they do change their spectrum towards a more algae growing spectrum...

 

[luconi]

Like green hair algae? or is it more like green coralline?

 

[tank202094]

is more like green algea.