Old Bulbs = Nuisance Algae?

[DanG]

as bulbs age, they can shift spectrum, so yes, old bulbs can contribute to nuisance algae. Have you measured your phosphates? What type of water do you use? RODI, RO, tap?

How old are the bulbs? You shouldn't have to change T5's till 9-12 months or so. Granted better bulbs should resist the colour shift better than cheaper bulbs, but there's no guarantee of that.