Bulb Life - Specifically Phoenix 14k

[JD46]

Interested in hearing some opinions on this one.

Background:

I have been running 2 Phoenix 14k bulbs in Giesemann Nova II fixtures for about 1 year. I upgraded tanks a few months ago and had to add another pendant. I bought the Giesemann pendants for the old tank because they would be hung straight from the ceiling and we in plane view. However, the new tank is in wall so I didn't feel like shelling out the extra cash for another Nova II. So, I bought a PFO and installed a new Phoenix. All ballasts are magnetic HQI; no electronics.

Finally to the point:

The general concensus on RC is that Phoenix bulbs lose intensity between 6-12 months. I installed the 3 pendants over the new tank and could not tell a difference in intensity between the old bulbs/Nova II's and new bulb/PFO. Brought home a light meter from work to test output to see if the older bulbs needed replacing. To my surprise, the Nova's actually had a higher reading (at a fixed distance below the pendants) than the PFO.

FYI, the light meter that I used read output in Watts. I have no idea how that correlates to lumens or PAR.

Question:

I understand that reflectors can cause variations in light delivery to the tank. But, if Phoenix bulbs lose their intensity over time, how can the old bulbs in the Nova II's be higher by 30-40% output? Is bulb life just a average time that people throw out there without truely knowing if the bulb has decreased it's output dramtically?

Thanks.

JD

 

[JD46]

Nobody??

I am wondering whether we tend to follow bulb replacement schedules blindly without truely knowing whether our bulbs need replacement. That could be a costly mistake at $60-$100 per bulb.

JD

 

[JohnK]

I think the lack of replies is due to the lack of a concrete answer. I don't know of any controlled testing that's been done on bulb aging, but they do age pretty quickly.

In general higher K temp bulbs will shift color quicker than lower K bulbs.

Also, IIRC the common reccomendations on bulb replacement times is more due to color shifting than loss of intensity. Bulbs tend to get less blue/more yellow over time. There may not be that much difference to the eye, but the color shifting makes for a constantly changing environment for the livestock on the tank. Again, IIRC, bulbs will stay pretty bright but the color will shift fairly quickly in the earlier part of the blulbs lifespan, as the bulbs get farther into their lifespan then the intensity starts to drop more.
A 10K bulb might keep firing for 2 yrs or more, but I think the consensus is that about 1 yr is the max you would want to run that bulb on a reeftank.

For your set up, I would guess that the different Mfg ballasts may have somewhat different outputs, and or the reflectors are making a difference as you mentioned. Overall though, with 14K bulbs I would think the lifespan is closer to 6 months than a yr.

 

[JD46]

Jimmyj

Thanks for the response. I think that your are right in that there is not a lot of knowledge on what happens to a bulbs output over time and how those changes will affect corals. Sanjay Joshi's lighting page provides valuable information on the spectral outputs of new bulbs. I would love to see similar information on bulb's output after use.

I think that you could be right that a constantly shifting spectrum may adversely affect the zooxanthellae's ability to photosynthesize efficiently. However, I did find this article published in Advanced Aquarist that summarizes zooxanthellae are able to use a wide spectrum to photosynthesize, so intensity is more important than spectrum.

http://www.advancedaquarist.com/2002/2/aafeature/view

The bottom line is that I hate being a lemming and following a "recommendation" without any data to support it.

JD

 

[Greg Hiller]

This is one of the reasons we now have a light meter in the club. Unfortunately, it has been VERY slow to move though the people who have been using it.

 

[JohnK]

Yes, I agree that overall intensity is more important than color, but anything constantly changing in a reef tank isn't necessarily good.

To add to what I said before, loosely paraphrasing a magizine article by Richard Harker,
lower K temp bulbs emit light over a much wider spectrum (duh) compared to higher K bulbs, but the lower K bulbs actually put out more blue (along with other peaks in the spectrum) than the higher k/more blue looking bulbs. The stronger blue just gets drowned out by all the other colors emitted.

This boils down to 2 things,
One blue bulbs are way weaker to begin with.
And two, the way the bulbs are made the blue/high K temp blubs degrade much faster because they use a much more limited combo of metal halides (I think that means gases??) and the ones the blue lamps use are the ones that degrade faster. The lower K bulbs use a wider range of halides and the not so blue ones last much longer.
In other words, Blue lamps are weaker to begin with, and they lose intensity much faster.
Blue lamps in general lose intensity very fast compared to wider spectrum bulbs. A 10K bulb may be servicable for a year, higher K temp bulbs generally fade way faster.

I guess I'm just reiterating the reasoning for the lemming thing that you mentioned, but trying to add on a bit of reason to support the frequent bulb replacement schedules that most people suggest/follow.

Also, I totally agree, some good research on the specifics of bulb aging would be very helpful. Unfortunately, if I understand correctly, every type of bulb is made differently and for that research to really be meaningful someone would like to do sanjay like testing on each specific bulb on the market, but do it over a year or so of use. That would cost crazy money and time so I doubt any one is going to do it.

Like Greg said, there is a club light meter, maybe there is a sign up or line to get into to borrow it?

I totally respect your concern about being a lemming, but form all I've read and heard, fairly frequent bulb replacement is the solid consensus throughout the reefkeeping community. FWIW/IME I have had a 10K ushio bulb that's run for over 2 yrs. I've also had 20K lamps die after 8-10 months. That says nothing about how the different bulbs degraded over those time tables, but the high K bulbs clearly don't last nearly as long. (the pheonix bulbs do have a fantastic rep for higher K bulbs, but still, I wouldn't trust them for more than 6-9 months - but maybe I'm just another lemming )

jk

 

[JD46]

jimmyj,

Once again, thanks for your input. Good discussion. I think that without the study that you outlined, there will be no way to truely tell the changes of different bulbs over time. So, the best you can do to take a leap of faith and follow the information out there.

Luckily, I have a light meter at work that I can use to keep tabs on bulb output.

JD

 

[Greg Hiller]

>for that research to really be meaningful someone would like to do sanjay like testing on each specific bulb on the market, but do it over a year or so of use.<

Sanjay is apparently working on some of this, but it will take time. There was some work done previously on the lifetime of bulbs, but much of it was done on bulbs that people don't use much anymore. FWIW, the Iwaski 6,500 K bulbs last just about forever!