Old bulbs = Algae problems?

[Delphinus]

Perhaps not a completely certainty, but it's a reasonably safe bet. I have no experience with Iwasaki's that old, so take that into account when I speak -- I've also used 10000K bulbs for over 2 years without algae problems but I would expect that to be an exception rather than the rule. Other bulbs I have used in the past (used several different ones over 5+ years in the hobby!), I could tell you exactly when they had hit "six months plus a day" because the difference was that apparent. Changing out the old bulbs caused the blooms to wither within days. So yes, I'd call it a "solid possibility." (How's that for a non-wishy-washy reply?)