Interesting Phoenix 14K results

[Mr. Fosi]

I posted this in my tank thread but I decided to post it here so it would get a little more play.

 

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In other news: I did a little geeking today regarding my lighting.

 

I borrowed the light meter from the lab (Li-Cor, LI-250A) and the 2π sensor (Li-Cor, Quantum) to measure the down-welling irradiance of my Sunpod at different points in/out of the tank. Yes, I know that isn't the waterproof sensor. I did a little modification to make it waterproof to the depth of my tank for the short duration of the measurements.

 

For reference:

- at noon on a sunny day at the equator, the down-welling irradiance is around 1500-2000 umol m^-2 s^-1.

- At noon on a very cloudy day here in SC, it can be as low as 50 umol m^-2 s^-1.

- Under the fluorescent lights you typically see used indoors it's up to 30 umol m^-2 s^-1.

 

Here are the most interesting numbers from my system:

Right at the glass UV shield: 3000 umol m^-2 s^-1

At the water surface (4.25" below glass): 1000 umol umol m^-2 s^-1

Just below water surface: 750 umol umol m^-2 s^-1

Bottom of the tank (14.25" below surface): 126 umol umol m^-2 s^-1

 

Here is a graph of the data along with a quantitative fit calculated by the PROFILE model that I've used for some of my research. The R² isn't bad but I generally see fits of 1.00 for the sediment oxygen data I usually use it on. I also successfully recognized the two different attenuation zones; above and in the water.

 

 

 

Fore more on the model I used for the fit, see the following reference:

 

Berg, P., Risgaard-Peterson, N., Rysgaard, S. (1999). "Interpretation of measured concentration profiles in sediment pore water." Limnology & Oceanography 43(7): 1500-1510.

 

You can see from the graph above that the light intensity drops off pretty quickly once you hit the water. The attenuation coefficient (including the air above the water) is 0.174 m^-1, 0.136 m^-1 without. According to a limnology link that I found, this value compares favorably with very clear freshwater. It also compares favorably with the coefs reported for a Honduras reef in:

 

Mishra DR, Narumalani S, Rundquist D, Lawson M (2005). Characterizing the vertical diffuse attenuation coefficient for downwelling irradiance in coastal waters: Implications for water penetration by high resolution satellite data. ISPRS Journal of Photogrammetry & Remote Sensing 60 (2005) 48–64

 

So the conclusion is that under a 150W Sunpod with a year-old 14K lamp, the corals in my tank are getting about as much PAR as they would if they were 14" or less below the water surface in a clear equatorial water body.

 

I guess I don't need to feel bad about not changing my lamp on the regular 8 month schedule.

 

EDIT: I almost forgot to add that the 20W halogen I use for the refugium puts off 1500 umol m^-2 s^-1 right at the glass, which is ~1.75" off the water which means it is probably on the order of 644 umol m^-2 s^-1 at the surface and maybe as much as 400 umol m^-2 s^-1 just below the surface. So, my chaeto is getting plenty of light too.

[MiddReef]

Very interesting Mr. Fosi....sometimes fish-lore and the technology of reefkeeping need a common sense and/or non subjective testing. Love that you included an R^2 value!

[Reefer Al]

That's extremely intriguing, I always assumed that reefers couldn't accurately replicate the sun's rays.. well I think you were measuring light intensity, or brightness? which isn't necessarily the only aspect of the light.. What aspect of light is there besides intensity and color?

[Mr. Fosi]

If you go to Li-Cor and look at the info about the meter and probe that I used, it returns data regarding intensity of Photosynthetically Active Radiation (PAR) which is a band of light wavelengths. Most PAR meters are biased against deep blue and purple light which is why PAR meters return low intensities when you try to measure the output of 20K lamps.

 

"Color" is how your eye perceives light and it can be affected by many things. "Spectrum" is a record of what wavelengths actually make up the light you see. I didn't report the spectrum here... Perhaps Sanjay Joshi has one in his database?

[southernfried]

Well then, color me happy that I chose to get a phoenix 14k 150 watt for my 29 gallon reef a week ago.

 

Thanks for the interesting post.

[Mr. Fosi]

Just for the heck of it, I decided to take a look at the 65W PC lamps I have over my lab tank. The lamps are at least 6 months old, purchased from hellolights.com and are 5" from the water.

 

"At the lamp" = sensor placed directly on the lamp.

"At the water" = actually about 1" above the water (too lazy to do temp water-proofing).

 

10K

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At the lamp: 606 umol m^-2 s^-1

At the water: 150 umol m^-2 s^-1

 

'05 Actinic

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At the lamp: 517 umol m^-2 s^-1

At the water: 100 umol m^-2 s^-1

 

The fixture isn't high-end. It's an Odyssea 130W and the reflector is a flat piece of mirrored aluminum. I imagine that a fixture with parabolic reflectors would be somewhat better, but obviously still nothing compared to an MH lamp.

 

I could get more PAR with a 20W halogen lamp than with 130W of PC... Of course the color(s) wouldn't look as pretty and corals seem to prefer more blue light, but the finding is interesting nonetheless.

[BumbleBeeJBG]

Very interesting stuff Mr. Fosi!

 

How would we see what the readings are from a natural reef x inches/feet down given a sunny day? Does the sun penetrate the water better than artificial lighting sources?

[BumbleBeeJBG]

Very interesting stuff Mr. Fosi!

 

How would we see what the readings are from a natural reef x inches/feet down given a sunny day? Does the sun penetrate the water better than artificial lighting sources?

[MitchReef]

Thanks Mr. Fosi....

 

That data supports what I have long felt....changing bulbs out too soon is a waste, and Phoenix ROCKS!!!!

 

I can only speak from my own success at growing and coloring up of corals....but I love those bulbs....

[Mr. Fosi]

How would we see what the readings are from a natural reef x inches/feet down given a sunny day?

 

You would need to dig up a primary or secondary reference for that. I am sure that some could be found fairly quickly using Google Scholar but I don't have the time to go digging. Rest assured, this phenomenon has been investigated ad-nauseum, you just need to find the references for it.

 

If you find some that look promising, post them here and I'll see if I can't get the PDFs or books.

 

All I have on-hand is a limnology book (not SW) and my physical oceanography book (theory).

 

The following table came from:

Knauss JA (2005). Introduction to Physical Oceanography. Waveland Press, Inc., p. 285.

 

 

 

 

You can see from the table that some wavelengths are absorbed by water more readily so talking about "light penetration" (look at the attenuation coefs; larger = quicker absorbance), you glaze over some distinctions. You probably already know that, barring the influence of biology, blue light travels furthest through water (which is why ocean depths appear blue) and that is borne out by the data in the table.

 

So then, talking about "light penetration" doesn't capture all the details about the penetration of various wavelengths, but it can still be useful. If you calculate the average of all PAR attenuation coefs in the table (400-700 nm) you get a mean coef of 0.196, which is actually a bit higher than I found in my tank. That means that, when speaking of PAR, my tank water is clearer than the clearest ocean water.

 

This shouldn't be too hard to believe since I don't have anywhere near an oceanic amount phyto or zooplankton in my tank and they can be effective light attenuators.

 

According to that data, 98% of the light entering the water would be attenuated within 5m in the clearest ocean water. If the ocean were as clear as my tank, 98% would be attenuated within 7.2m. Obviously, some light penetrates much further than 5m in the ocean, but it is orders of magnitude less than is found at the ocean surface and it is an increasingly small subset of wavelengths.

 

If you want to know how that compares to FW lakes of varying trophic states (i.e. plankton and nutrient loads), look at the limnology reference I posted in the first post.

 

Does the sun penetrate the water better than artificial lighting sources?

 

Light is light and it will behave the same whether it is from the Sun or from an MH lamp. Having said that, MH lamps as we use them are not simple black-body light sources because we use reflectors. This may have some effect on light penetration, perhaps by increasing the spectral reflectance to penetration ratio.

 

This doesn't appear to be the case, according to the table above and the calculation I performed using it. However, you might be able to find a primary reference that is a bit more empirical.

 

Mitch: This data doesn't say anything about the intensity degredation that the lamp may undergo over it's life. It may me that the lamp puts out a significantly higher amount of PAR when it is new.

 

This doesn't change the fact that after a year, they are still good (with regard to PAR intensity) for use in reef tanks.

 

EDIT: For reference, here is a figure that depicts some of the elements that attenuate light in natural waters.

 

[SeeDemTails]

Very interesting indeed. One of my bulbs is older than 2 years now, and it is still growing the crap out of corals.

[Mr. Fosi]

Wanna send it to me so I can measure the PAR intensity?

[SeeDemTails]

Wanna send it to me so I can measure the PAR intensity?

 

I would but I need it as a back up! When I buy another bulb to replace the newer of the two I will send it to you though!

[Mr. Fosi]

Sure thing, but I bet you won't replace it until it burns out or blows up.

[Kool-cat]

How often should you change your bulbs out? I changed my phoenix after 12 months now. I changed it after 14 months before and my corals didn't really like it when the new bulb was illuminating over them. I had to put screening over my tank to reduce the light.

[Mr. Fosi]

Who knows? I guess it depends on your wallet, your livestock and your willingness to re-acclimate them.

 

Your corals' reaction suggests that there is a significant reduction in PAR over 14 months.

 

You don't happen to have your old lamps do you?

[Kool-cat]

Who knows? I guess it depends on your wallet, your livestock and your willingness to re-acclimate them.

 

Your corals' reaction suggests that there is a significant reduction in PAR over 14 months.

 

You don't happen to have your old lamps do you?

 

 

I got a 12 month old and a 14 and a half year old phoenix bulbs.

[BumbleBeeJBG]

I wonder if the ballast will effect bulb life? Something like electronic vs. magnetic?

[BumbleBeeJBG]

I wonder if the ballast will effect bulb life? Something like electronic vs. magnetic?

[Kool-cat]

I heard the magnetic ballast will overdrive the bulb causing it to lose its useful life quicker.

[Mr. Fosi]

I got a 12 month old and a 14 and a half year old phoenix bulbs.

 

Want me to test them and see if the PAR differs from mine? I won't do a full water test since the attenuation can be calculated using what I have already provided but I would test it in the air at the same distances I did with mine.

 

You pay the shipping to me, I'll pay the shipping back. If you're interested, PM me.

 

I have a bunch of fluorescent lamps who's spectra I want to compare but that is more complex and requires a more replicatable rig to make the measurements. PAR is much simpler to measure and to be repeatably accurate and precise.

 

I wonder if the ballast will effect bulb life? Something like electronic vs. magnetic?

 

It might. I confess I don't know much about ballast types and what their differences are, which is why I stated what fixture I used in these measurements.

[Scott Riemer]

I wonder if the ballast will effect bulb life? Something like electronic vs. magnetic?

We need to get to the bottom of why you seem to be double-posting so much. Not saying it is your fault.

[BumbleBeeJBG]

We need to get to the bottom of why you seem to be double-posting so much. Not saying it is your fault.

 

It's happening on two message boards I frequent and it's damn annoying. Which means it's on my end, I'm on it don't worry.

[Mr. Fosi]

I think this is good news for those of us that have a hard time springing for an $80 lamp every 8 months. The fact that these lamps still have a great PAR intensity and others have shown them to have little or no color shift makes these lamps a great choice for the reefer on a budget.

 

I wonder how other MH lamps compare. 20K lamps for instance.

[ssirishpride]

I would like it if you could run your testing on a couple of 250w eBay specials I have laying around. I am curious to know the results of a "high end" VS. "inexpensive" Both have 7 days of use on them. I am currently running another one of the 20k's and it seems a bit "white" compared to the Hamilton, Phoenix and Current lamps from past replacements. Are ya interested, I have a 14k and a 20k?