Old bulbs = Algae problems?

[Delphinus]

Christy, I assume you mean you saw NO decline in algae growth?

PS. I didn't mean to suggest that old lighting was the only cause, just ONE potential cause. Definitely for "due diligence" all those other possibilities should be explored as well. However, that said, two years on a halide IS pushing it. Although I am as guilty as anyone for doing that, there's no doubt that after two years of solid use (espescially assuming something like a 10-12 hour daily photoperiod), it's not gonna hurt ANYthing (except maybe the wallet) to replace those bulbs.