400w bulb

[mandm25254]

how long would you use a 400w bulb on 7 hours a day?

[SlowCobra]

Most of a bulbs life is lost in the first 2 months or so. It is a very slow decline of par after that. Usually most people will replace them after 12 months.

[mandm25254]

thanks any more saggestions

[MJAnderson]

Originally posted by SlowCobra
Most of a bulbs life is lost in the first 2 months or so. It is a very slow decline of par after that. Usually most people will replace them after 12 months.

What other suggestions are you looking for? If you don't replace them every 2 months you can run them until you get tired of them or the spectrum shift produces color you don't like. I think they lost 10-15% the first 2 months then 2-3% after that at a fairly constant rate.

[chk4tix]

So bulbs really decrease that much within the first 2 months?

[MJAnderson]

Here's the article

http://www.reefkeeping.com/issues/2007-04/ac/index.php

And the summary:

The light output of the six Phoenix bulbs shows an initial decline over the first three to four months and then levels off at about 75% of their initial output. From these data I raise the question: “If a bulb is not replaced at six months, when it has lost 20% of its output, then why would we replace it at 12 months when its output has fallen only another 6%?” It may be more cost effective to plan the lamp number and placement based on 70-75% of the bulbs' initial output levels. Initially, we could shield or raise the lights and then gradually lower or unshield them over the first four months or so, when the intensity is at its highest but falls most quickly. Beyond six months the bulbs' light output remains fairly constant at about 75%, so only minor adjustments would be needed for at least a year. Doing this may considerably extend the bulbs' effective life.