When should I change bulbs?

[Varga]

they are 250W DE HQI 1400k cheap Chinese brand and about 10 months old.

they are still pretty white and corals are still growing.....how does one know when one should change one's bulbs?
Is there a set date or is there signs I should look for?

Thank you

[Frankie]

I change out every 6 months. Some people go 8. Your well over due imo.

[Varga]

WOOOO I had no idea I need a loan

[Varga]

so does the rated hours meqan anything? one of them says 9000 rated hours!

[Frankie]

I am sure it does. I have always stuck to the 2x a year change out like suggested in the past and it has not failed me yet. HQI bulbs might be different. I am hoping someone with real knowledge on them will chime in on this~
XM's lasted me under 6 months and I saw them shift in under a week. THe quality of the bulb has a lot to do with it I am sure.

[Varga]

You've got to check this out:

Light Output of the Phoenix 14,000K DE MH Bulb Over Time by Allen Chantelois - Reefkeeping.com

[Frankie]

Thanks. I book marked it for tonight.

[lcstorc]

Very interresting article. I will have to bookmark it.
Certainly not scientific but I run 150w XM DE bulbs for my lighting and when I replaced them after 9 months there was a considerable difference in appearance as well as coral growth. Just my experience.

[mps9506]

Gotta take into account your photoperiod and ballasts when deciding when to change your bulbs. Someone running their bulb 4 hours a day can probably go twice as long as someone running 8 hours a day. HQI ballast, or electronic ballast will make a diff as well.
and also noting that article linked above, intensity is only part of the story.

Of course, light intensity is only part of the story. I had no way of accurately assessing the changes, if any, in the bulbs’ spectral shift.

You need to account for changes in spectrum as well.