Old Bulbs = Algae

[wickedfrags]

No significant correlation between bulb age (or spectrum) and algae growth in my experience. Water quality (nutrient levels) dictates algae growth, not quantity or spectrum of light.

Originally Posted by Tyler Werbowski

I understand that older bulb lose intensity and there's a slight spectrum change. I've heard that old MH bulbs can be a contributing factor to unwanted algae growth. Could someone explain the theory behind algae growth?