how often do you change your PC lamps

[Richer]

I've been running the same PCs (4x55watts) over my plant tank for 2.5 years. There is a very noticable differences in the brightness of the fixture. It is quite a bit dimmer now then it was 2.5 years ago. To the point where, I don't need to run my CO2 injection system on the tank anymore and it still looks fine. Back then, my entire tank would be covered in algae if I delayed refilling my CO2 tank for a couple of days.

So even if the spectrum stays the same, I would still replace bulbs after 8-12 months just to keep the brightness level at around the same level.

-Richer