How often does everyone else change your HPS/MH bulbs and tubes. I've been doing it every 6 months or so and it's easier to remember and while I'm at it the filters get changed on the RO system too. The footcandles went up 500 fc with the change so I guess it was time!

I change mine every 2-3 years.

Peter, are you lowering the light fixture to make up the difference? Or is not your only source of light. Have you checked with your light meter lately?

I try to change the bulbs in my MH fixture and fluorescents once a year or slightly longer. For the HPS fixtures I let them go two years or longer.

e-spice

once a year for me

Peter, are you lowering the light fixture to make up the difference? Or is not your only source of light. Have you checked with your light meter lately?

No natural light, not lowering the lights and my HPS is the only source of light and nope I do not use a light meter. My plants are still growing and blooming like clockwork.:D

Guess I'm toooooo fussy!:)

I have found a local hydroponics store that does replacement bulbs cheap.
I have tested the output with my light meter & they are @ least as good as the Philips HPS i had originally for foot candles.
As for light spectrum , well my paph roths & roth hybrids are spiking so that is all i require .
I do have a Ceramic Metal halide that has a "natural" sunlight spectrum but using it horizontallly looses quite a lot of foot candles so i swap to this for a week or so before i put them out in the g/h.
I will get a replacement HPS bulb around Feb , the same as this year.

For what it's worth, half of my bulbs are HPS and the other half are MH. I change them every two years, but I do it on a rotating basis. For example, this year I am replacing all of the MH bulbs, and next year I will replace all of the HPS bulbs, etc. Just for fun, you might want to look at the Hortilux Blue MH bulbs manufactured by Eye; they seem to be the closest in matching the visible spectrum of natural sunlight of any plant growth bulb that is manufactured. I was quite impressed by their data--or, maybe, I am just a "sucker" for their "spin."