mh look difrent colors from day 2 day

a monthand a half ago i bought mh the bulbs have been burned in but today one of the lights was a lot bluer than usual was wondering if that was common:-/

 

Metal halide bulb have a break in time where you will notice a change in color from the first time you turn them on til they break in! Normal!!!

 

Completely normal. Ambient air temperature can also it somewhat too. It usually takes anywhere from 20 hours up to 200 hours to break in fully. Mine started out very blue (14000K bulbs) and now give off more white color than when it was brand new. It's normal, just remember to change them near the year year mark if you run them 8 hours a day or less, 8 months if you run then more than 8 hours. I run my HQI for 8 hours and MH 7 hours a day (I don't have corals) and was told that my bulbs should be good for about 14 months at that usage.

 

Very true, I know from experiece that commercial MH lamps sometimes take 100 hrs to burn in to the final color so I would imagine the same is true of the lamps we use in reefkeeping.