How long do Metal Halides last?

narkfish

Member
I have two 20K 150 watt metal halide light bulbs. I have had them for a year and a half now. How long till I should change them, and will it greatly effect the growth of corals?
 

snakeblitz33

Well-Known Member
I read somewhere that metal halides should be replaced once a year. The problem comes from the light spectrum shifting more towards the red zone, causing the corals not to grow as efficiently and causing algae problems. As a precaution, regardless of what kelvin they are, I will go ahead and replace my metal halides once every year to year and a half. I think I also remember where old bulbs can wear down ballasts and they will start to "cycle". Your bulbs will turn off and on all the time at the end of the bulbs life.
 

snakeblitz33

Well-Known Member
I'm pretty sure Corey and Henry (2Quills and Spanko) will know a lot more about it then I do off hand. But, that's just what I know or have been told over the years. They get more technical. :D I hope I helped some. :D
 

2quills

Well-Known Member
They should be changed every 8-12 months to maintain efficiency and avoid large spectral shifts. On average I believe they lose something like 30% of their efficiency within the first few months of use and it only goes down from there. So I'd change them at least once a year. Some guys change them twice a year (every 6 months). :p
 

reefraff

Active Member
20K 150 watt halides have really crappy PAR. If you are raising high light critters in a tank over 16 inches tall twice a year is a pretty good idea.
 

narkfish

Member
Great thanks that all helped a lot, Although what is meant by PAR? Would something like a 14K be better for growing things?
 
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