When to REALLY replace Metal Halides

[mobyreef]

I have read, and pretty much understand, par as a measurement to determine photo synthetically active radiation, But... I don't have a par meter.
I DO have a photographic light meter which doesn't read par but does read brightness ect. I also have a color temperature meter that I have on-order (It's old but Cheap). Is there any way to use my photography light meter to determine when my metal halides are Really needing to be replaced? When I get my color temperature meter I will see if the 14k bulbs are still 14k. Am I missing something about par? Is it a meter I really should be using? I noticed that Marine Depo & Bulk reef supply don't carry them in stock. Where can I one buy one? I just hate to throw away a bulb that still fires and still looks blue after a year of use just because they say to replace them every 8 to 12 months! Any enlightenment on the subject will help and possibly save me some coin as well.

Thanks for any help.

 

[n0rk]

I doubt your 14K bulbs are anywhere remotely close to a true 14K for what it's worth replacement schedule is just a suggestion, the best bet is to look for signs from the corals themselves - reduced growth, colour changes, decreased PE, browning out, etc, etc. A meter is definitely handy to have and will tell you much about how linearly your light's output has fallen, but it won't tell you everything.

It also comes down to many other factors as well... ambient temperature over its effective lifetime, ballast spec, bulb brand, claimed colour spectrum, phosphors used... too much to call it from gut feeling