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How to Tell if a Bulb is Old

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How can I tell if a reef bulb has much usable life remaining? My upgrade system came with 250-watt DE MH bulbs and 40-watt VHO bulbs. I suspect the bulbs are not super recent. The previous owner also gave me three 250-watt bulbs that are inside boxes, but I can't tell how much usable life those have either. Are there any visual signs that a bulb is too old? Is the only way to really tell about a bulb's effectiveness to borrow a PAR meter? The bulbs in the boxes seem to have a blackish coloring around the center... I'm assuming that those are used.
 
It depends on the kelvin, the lower the k the more difficult to tell, if they are 14-20k bulbs look for splattering inside the envelope that's a sure sign they've been used for a while. Also, sometimes it's not just a matter of actual age, but whether or not the bulb was run on the proper ballast, for example SE Ushio bulbs are best run on magnetic ballasts, they last a long time when run on those ballasts as compared to an HQI ballast, on the flip side you have the Radium which lasts longer when fired on an HQI versus a standard magnetic ballast.
 
Some bulbs are pre-burned prior to you getting them. It takes so many hours for a bulb to burn in so some companies will pre-burn them in.
 
Good point Gresham, I'll clarify, heavy splattering that looks blac/silver that can coat the inside of the envelope, not just a slight charring on the ends.
 
Wow, so many factors to consider! No wonder tank journals are really important to be able to gauge the effectiveness of things like bulbs. The MH bulbs that I have are 20K, and I'll need to look more carefully at the ballasts.

Gresham, do you think the slighly black coating around the center area is the sign of pre-burning of the bulbs? Or is that the splattering that Jeremy mentioned that shows the bulb is well-used? Is the envelope the part in the center of the DE bulb where the light actually is concentrated?

I will email the previous owner, to see if he remembers anything about the age & amount of use the bulbs have.
 
I've been wondering the same thing... Without a par meter, what do people do? Wait for funky algae growth? Just change them routinely every X number of months? There must be a better way.
 
I change them out every 6 - 8 months depending on when I get around to it.
 
They have less color shift but last just as long as the higher kelvin bulb IIRC.
 
What type of ballast over another can shorten bulb life (now how significantly that is up for discussion) - one more thing to factor in
 
I use a PAR meter to see how much loss over 6-12 months in PAR there is. That plus the look of the bulb are the 2 factors. I have 20K bulbs and unless my eyes are wrong, they seem to lose the blue color over time and look more white. A PAR meter doesn't help much unless you know the PAR when the bulb is new so you can compare the value.
 
Nope, your right. 20KK will shift down over time. Most bulbs will but it's really noticeable in 20KK.

In my last post I should have said, "they have less of a noticeable shift then 20KK bulbs"
 
I've noticed 20k bulbs get more noticeably dimmer as well as shift more dramatically as they age, again though it is super duper important to note what type of ballast the bulb is designed to fire on.
 
It turns out that the 20K bulbs in my new lights (which have magnetic ballasts) are 8 months old, and the other bulbs inside the boxes are also used, based upon the amount of black coating inside of them. Before disposing the used bulbs, I learned that it is a good idea to keep a spare set, in case something happens and the reef owner needs to wait for new ones to arrive in the mail.
 
I typically replace my bulbs every 6 months and then keep the old ones for spares as they usually have a decent amount of life left in them.
 
From what I have gathered over the years from other peoples reply to bulb life of high kelvin bulbs, is that a good rule of thumb is to replace your bulb every ~ 1500 hrs of normal use. or... approximately 4mo at 12hr/day , 6mo @ 8hr/d, 8 mo @ 6hr/d, 12 mo at 4hr/d. Again, a guide, not a rule.
 
Tony, thank you for summarizing the rough guide to replacement of high kelvin bulbs. I really like the look of the 20K bulbs in my new system, which are 8 months old. That means that it is probably time to replace them, assuming they have been on for roughly 6 hours/day. Then I, like Gresham, will have two extra old sets of MH bulbs!
 
Gomer said:
From what I have gathered over the years from other peoples reply to bulb life of high kelvin bulbs, is that a good rule of thumb is to replace your bulb every ~ 1500 hrs of normal use. or... approximately 4mo at 12hr/day , 6mo @ 8hr/d, 8 mo @ 6hr/d, 12 mo at 4hr/d. Again, a guide, not a rule.
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A guide to be sure, firing MH bulbs ages them, when they are on, not so much ;). So shorter light cycles does not necessarily = longer bulb life like with fluorescent bulbs.
 
Burning them ages as well. You end up deteriorating the electrode tips. (this isn't to say that simply turning on and off isnt bad :))
 
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