Old Bulbs = Algae?
- Thread starter NaH2O
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Boomer
Well-known member
Yes Mike I will go with that BUT shifts in wave length will change the K, as wave lengths and the amount of wave length x,y or z determine K. Phosphors degrade, which will shift the K. This comes with time. Any light bulb will have a **** in K in the first 100 or so hrs of operation, same for output. So, it is not just an output shift. Think of K as a bucket of red paint. A 1 gal bucket will be the same color or K as a 10 gal bucket but if we start adding white paint (degrade phosphors)to either the color will change. Most light bulb output drop to 60 % in 6 months.
The main failure mode for florescent bulbs (assuming you don’t brake them) is from depletion of the electron emission coating found on the electrode/filaments. The filaments used in fluorescent bulbs are normally tungsten coils coated with a special material (typically barium oxide) that emits lots of electrons when heated (~ 1300K). When this coating on the filament is gone the bulb can no longer maintain the electric arc in the tube. On top of this electrode failure mode it is also possible to lose bulb light intensity over time or have the effective color temperature shift. These reductions in a bulb’s light performance over time can be caused by a several factors including degradation of the bulb’s phosphors, darkening of the tube’s glass (both due prolonged exposure to UV light and the elements generating it) and evaporation of the coatings use on the electrode’s filaments (which in turn can react with mercury and cause darkening of the bulb near its ends). Phosphor degradation rate will depend on several things including the specific phosphors used as well as the bulb wattage relative to its surface area. This means that the light properties of tubes using higher wattages for a similar sized tube such as High Output (HO) and Very High Output (VHO) bulbs will normally degrade faster than standard output bulbs. Most standard output florescent bulbs claim 10,000-20,000+ hour operating lifetimes but can fall to 80% or less of their original light intensity after 10,000 hours operation. Depending on your requirements for light intensity and color fidelity you may need to replace bulbs more often than indicated by full failure lifetimes.
One additional comment concerning florescent light bulbs – while the mercury vapor inside the bulb produces UV light when excited, little UV radiation is emitted outside of conventional bulbs due to both its absorption by the phosphors on the inside and also the fact that glasses typically used for tubes block most UV light.
Here are some age comparisons
http://www.personal.psu.edu/faculty/s/b/sbj4/aquarium/articles/MetalHalideLamps2.htm
The main failure mode for florescent bulbs (assuming you don’t brake them) is from depletion of the electron emission coating found on the electrode/filaments. The filaments used in fluorescent bulbs are normally tungsten coils coated with a special material (typically barium oxide) that emits lots of electrons when heated (~ 1300K). When this coating on the filament is gone the bulb can no longer maintain the electric arc in the tube. On top of this electrode failure mode it is also possible to lose bulb light intensity over time or have the effective color temperature shift. These reductions in a bulb’s light performance over time can be caused by a several factors including degradation of the bulb’s phosphors, darkening of the tube’s glass (both due prolonged exposure to UV light and the elements generating it) and evaporation of the coatings use on the electrode’s filaments (which in turn can react with mercury and cause darkening of the bulb near its ends). Phosphor degradation rate will depend on several things including the specific phosphors used as well as the bulb wattage relative to its surface area. This means that the light properties of tubes using higher wattages for a similar sized tube such as High Output (HO) and Very High Output (VHO) bulbs will normally degrade faster than standard output bulbs. Most standard output florescent bulbs claim 10,000-20,000+ hour operating lifetimes but can fall to 80% or less of their original light intensity after 10,000 hours operation. Depending on your requirements for light intensity and color fidelity you may need to replace bulbs more often than indicated by full failure lifetimes.
One additional comment concerning florescent light bulbs – while the mercury vapor inside the bulb produces UV light when excited, little UV radiation is emitted outside of conventional bulbs due to both its absorption by the phosphors on the inside and also the fact that glasses typically used for tubes block most UV light.
Here are some age comparisons
http://www.personal.psu.edu/faculty/s/b/sbj4/aquarium/articles/MetalHalideLamps2.htm
Scooterman
Well-known member
Where are you when I'm trying to explain that to people? lol
I was trying to explain that just because a fluorescent still burns bright at two years like they claim for the T5, doesn't mean the affective light is useful in a reef aquarium but now I can link over to this page, thanks.
I was trying to explain that just because a fluorescent still burns bright at two years like they claim for the T5, doesn't mean the affective light is useful in a reef aquarium but now I can link over to this page, thanks.
Boomer - if I understand the bold section of your post correctly, the color shift in flourescents is an apparent shift resulting from a preferential decrease in some wavelengths rather than an increase in output for some wavelengths. So, if some wavelengths favor certain nuisance algaes, then the effect of old bulbs would not necessarily be an increase in nuisance algae, unless (possibly) the decrease in other wavelengths resulted in less nutrient consumption by other (more desirable) tank inhabitants (making more food available for the undesirable algaes).
Boomer
Well-known member
Scoot
Where are you when I'm trying to explain that to people?
Randy was gone for a week so I had to babysit the forum
Don
Yes and I really don't see how one would get an increase in output of other wavelenghts. The K always drops with aging, mostly due to lower output
Where are you when I'm trying to explain that to people?
Randy was gone for a week so I had to babysit the forum
Don
Yes and I really don't see how one would get an increase in output of other wavelenghts. The K always drops with aging, mostly due to lower output
Boomer
Well-known member
Yes, but I don't really think one can really blame light shift/ K /color on cyano. I think there is more to it than that, such as nutrients, ORP, current, etc..
No, not if I understand the process correctly. For flourescents anyway, the individual peaks don't shift to different wavelengths. The peaks decrease in magnitude more at the lower wavelengths (blue) than at the higher wavelengths (red), making an apparent shift of the whole. But no individual peaks actually shifted.mojoreef said:
Looking at that link to Sanjay's testing of 400w MH bulbs basically shows the same things for the MH's. Wavelengths in the blue range decreased in intensity a lot, while wavelengths in the red range were practically unchanged (at least for the limitations of his testing).
Scooterman
Well-known member
dnjan said:
That is why 6.5k lamps are tested higher PAR
The individual peaks not shifting (for flourescents) is why I asked Boomer for clarification earlier.
For Sanjay's testing of older 400w MH bulbs, see Boomer's post on the second page of this thread. Partway down the page. The post with the long quote in bold. Right under the quote, he gives the link to Sanjay's testing (not in bold). When you look at Sanjay's results, you will see peaks moving up or down (almost all down with age), but they don't shift (to the right, or longer wavelengths).
For Sanjay's testing of older 400w MH bulbs, see Boomer's post on the second page of this thread. Partway down the page. The post with the long quote in bold. Right under the quote, he gives the link to Sanjay's testing (not in bold). When you look at Sanjay's results, you will see peaks moving up or down (almost all down with age), but they don't shift (to the right, or longer wavelengths).
The 6500's and 20k radiums look like they have the biggest changes on the left half (of the spectrum) and not as much on the right. Harder to see with the 10K, but that series had some pretty screwey results for one of the ages.
But the important point is that the peaks don't appear to shift to the right for any of the bulbs/ages.
But the important point is that the peaks don't appear to shift to the right for any of the bulbs/ages.
