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How long does one go before they switch out their bulbs? 9 months? a year?
When to change MH lighting?
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some people go as short as 6 months some go until they burn out. I'd say the average is about once a year. The higher the rating of kelvin the quicker your bulbs will diminish since the blue and green spectrums are the first to burn out. I try to replace the halides at seperate times than my pc's though. Its not as shocking to the tank.
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Hrmm, I know Mojo said actinics don't need to be switched, but based on what you said, does that mean they need to be switched out more often than MH's?
Not all PC's are actinics.... 
The best way to do it (and most cumbersome) would be to measure the PAR after ~50 hrs of MH use and then every month. When the PAR drops below a certain value (90% of new? 80% of new? - whatever your threshold is), then it's time to replace.
Of course, this requires you to have a PAR meter on hand...
The best way to do it (and most cumbersome) would be to measure the PAR after ~50 hrs of MH use and then every month. When the PAR drops below a certain value (90% of new? 80% of new? - whatever your threshold is), then it's time to replace.
Of course, this requires you to have a PAR meter on hand...
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But is it the PAR that deteoriates or is it the spectrum shift that's the problem? I always thought it was the spectrum shift.
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mojo wrote: Not all PC's are actinics....
The best way to do it (and most cumbersome) would be to measure the PAR after ~50 hrs of MH use and then every month. When the PAR drops below a certain value (90% of new? 80% of new? - whatever your threshold is), then it's time to replace.
Of course, this requires you to have a PAR meter on hand...
I should have a PAR meter on hand, all the cool kids have em:sad:
To my knowledge, it's both spectrum shift and loss of overall intensity. I believe that the spectrum shift will change the color and your perception of the corals, but intensity will change their growth rate. They should be fairly closely matched, so one will be indicative of the other.
PAR is the measurement of quantum flux between 400-700nm usable by zooxanthellea. PAR measures usable photosynthetic light so as the bulb shifts spectrums it should reduce PAR. Don't know for sure since I haven't tried, but makes sense. Maybe one of the practical experts could debunk that statment.
I don't think anyone can say for sure without doing some very controlled and well-executed tests. My *guess* is the following:
- corals will continue to grow at the same rate based on the amount of PAR received over a full day. 200 PAR * 7 hrs = 1400 PAR hours. If the intensity drops, and you only get 150 PAR, then you'd need a light cycle of 9.3 hrs (150*9.333 = 1400) to reach the same amount of energy, irrespective of spectrum shift.
- Spectrum shift will affect our own perception of the corals and most likely affects the colors produced in the tissue of the corals.
- Since most people don't have a PAR meter and far fewer have a spectrometer, we have to base our assumptions on what we do know - spectrum and intensity change over time.
Therefore, if you have a PAR meter, you can watch the PAR drop over time and note when it's time to change the bulb based on intensity alone. If the corals lose color within the timeframe you've set, then you'll have to shorten your bulb change schedule.
To answer your question, PAR and spectrum will affect the colors of the corals. If your intent is to keep the same colors, you'll need to replace the bulbs on a regular schedule, regardless of what factor actually causes them to change color...
- corals will continue to grow at the same rate based on the amount of PAR received over a full day. 200 PAR * 7 hrs = 1400 PAR hours. If the intensity drops, and you only get 150 PAR, then you'd need a light cycle of 9.3 hrs (150*9.333 = 1400) to reach the same amount of energy, irrespective of spectrum shift.
- Spectrum shift will affect our own perception of the corals and most likely affects the colors produced in the tissue of the corals.
- Since most people don't have a PAR meter and far fewer have a spectrometer, we have to base our assumptions on what we do know - spectrum and intensity change over time.
Therefore, if you have a PAR meter, you can watch the PAR drop over time and note when it's time to change the bulb based on intensity alone. If the corals lose color within the timeframe you've set, then you'll have to shorten your bulb change schedule.
To answer your question, PAR and spectrum will affect the colors of the corals. If your intent is to keep the same colors, you'll need to replace the bulbs on a regular schedule, regardless of what factor actually causes them to change color...
Good points and makes sense to me at least. The one caviat that I would mention is that if your corals are past the light saturation point (I have no idea what that is and depends on the coral type being kept) they won't grow any less from the diminished light until light saturation is no longer met. As you stated however, there color could (and probably will) change.
I learn more every day.
I learn more every day.
You can do some reading up on Dana Riddle's work regarding light saturation points; look for his papers on the Advanced Aquarists website.
He gave a really good presentation a while back to the ARC about all this. To summarize his presentation- all corals tested max out at 350 PAR or less. He could not find a limit on Tridacna clams with the equipment he had (either 1500 or 2000 PAR - I can't remember).
He gave a really good presentation a while back to the ARC about all this. To summarize his presentation- all corals tested max out at 350 PAR or less. He could not find a limit on Tridacna clams with the equipment he had (either 1500 or 2000 PAR - I can't remember).
I will add it to my read list as the next set of work to read. Currently, I am making my way through Borneman's Aquarium Corals and a couple electronics books to make sure I calc the LED array I am working on correctly. I think my head is about to explode from all this information. Just when I think I have a handle on it, there is another corner with 12 more volumes of info to sift through.
When I am done with this LED thing, I wouldn't mind taking PAR readings to see what I get. Do you have a PAR meter and time for a free meal when I get this thing done?
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So uh.... 9 months?
Everything you ever wanted to know about the shift... whew what a set of articles:
http://www.personal.psu.edu/sbj4/aquarium/articles/MetalHalideLamps1.htm">http://www.personal.psu.edu/sbj4/aquarium/articles/MetalHalideLamps1.htm</a>
[IMG]http://www.personal.psu.edu/sbj4/aquarium/articles/MetalHalideLamps2.htm">http://www.personal.psu.edu/sbj4/aquarium/articles/MetalHalideLamps2.htm</a>
[IMG]http://www.personal.psu.edu/sbj4/aquarium/articles/MetalHalideLamps3.htm">http://www.personal.psu.edu/sbj4/aquarium/articles/MetalHalideLamps3.htm</a>
I don't know how true it is, but it seems if you get a good bulb it will run 18 months before a significant drop occurs from their testing. I think 12 months is reasonable and earlier than that if you feel like it. Course this is based on there one study so it is a one source opinion.
http://www.personal.psu.edu/sbj4/aquarium/articles/MetalHalideLamps1.htm">http://www.personal.psu.edu/sbj4/aquarium/articles/MetalHalideLamps1.htm</a>
[IMG]http://www.personal.psu.edu/sbj4/aquarium/articles/MetalHalideLamps2.htm">http://www.personal.psu.edu/sbj4/aquarium/articles/MetalHalideLamps2.htm</a>
[IMG]http://www.personal.psu.edu/sbj4/aquarium/articles/MetalHalideLamps3.htm">http://www.personal.psu.edu/sbj4/aquarium/articles/MetalHalideLamps3.htm</a>
I don't know how true it is, but it seems if you get a good bulb it will run 18 months before a significant drop occurs from their testing. I think 12 months is reasonable and earlier than that if you feel like it. Course this is based on there one study so it is a one source opinion.
