Hydra52 Par vs Power study

[Wazzel]

I decided to run a basic study with my Hydra52 to see how power and par are related. While I was at it I also look at how each channel impacts total par.

Equipment
Hydra52 8" above water line with all pumps off
AI director for control
Apogee MQ-200 sensor 18" below light, 10" below water line

Test procedure
First step was to take readings with all LEDs at the same setting. I started at 10% power and worked up to 100% in 10% increments and recorded the uncorrected values.
Second step was to take uncorrected readings for each channel from 10% to 100% power in 10% increments.
Third I summed the individual reading to see if they would agree with the full sets of readings. The summed values are close to the full readings.
Fourth I looked at the power per channel as a function of the total for each power setting.

Results
Keep in mind these are uncorrected values. I was looking for relative values, not absolute. The only way I could compare the individual channels to the all channel numbers was to leave them uncorrected.
Power vs par is fairly linear. I would call it linear with the fairly coming from some minor blips in the meter readings.
Par per channel is relatively constant no matter the power setting, if all channels are set to the same level.
White is the biggest contributor to Par when all channels have the same power value. In decreasing order of par Royal Blue, Deep Blue, red, violet, green, UV.
Red, Violet, Green and UV make up about 14% of the total Par together.

Hope this helps.

 

[slief]

Interesting and great testing. I can see this being very useful for many here. The only thing that is misleading which I am reasonably sure you are aware of is the par on the darker blue channels. Consumer grade PAR meters like the Apogee have issues reading par on the deeper blue to UV spectrum led's. After about 460nm, the meters readings really drop off. This isn't due to a lack of PAR but more so to the sensors ability or lack of, to read that spectrums intensity. More interestingly is that much of the photosynthetic light that our corals utilize come from those wavelengths.

From the looks of your tank picture, it looks like you even shut your pumps down so the waters surface was calm. Am I correct in that assumption? Good work by the way, I would be great if the same could be done for other popular lights like the Radions, Kessils, Reef Breeders etc., so we could have some good comparisons. Only issue is that it would really need to be done over the same tank so that the results were on a truly controlled environment.

 

[Wazzel]

I am trying to not mislead, which is why I made sure to state these are uncorrected measurements. Apogee has some correction factors. I am also aware of the reading window of the sensor. There is upper (655nm) and lower (410nm) bounds that the sensor works.

I did indeed turn off all my pumps to get a still water. I did a water change yesterday so things should have been clear as possible. I do not think it would need to be done over the same tank. My idea was to provide some relative information to help others set their lights and get some understanding of how things work together. I was not really looking to compare across fixtures.

I have put out some feelers for other LED light fixtures on our local (Louisiana) reef board. If I can find some a reasonable distance from my house I would do those also.

 

[DasCamel]

Looks fairly linear. Nice work!

 

[awdjosh]

Wazzel, thank you so much man. I actually did a PAR reading on my sps dominant tank today and was shocked that my current light settings were the cause of everything doing so badly after a couple months and such slow growth, never will I just take advice to others when they say never turn these lights over 75% -_-

Also set each percentage on the spectograph to match what the corals need for chlorophyll A&B and retested to find almost spot on par numbers of what the coral needed.

Im in pensacola fl not far from Louisiana, pm and we can swap some frags in the future.

 

[Wazzel]

Josh. Glad this was helpful. Lots of thing get passed on with out real understanding of what is going on. I suspect lots of the recommendations to keep the lights down was for people turning them up to fast. It is real easy to burn corals with LED lights if you are not careful. That does not mean they should stay low forever.

We will have to see about swapping frags. My tank is not yet a year old. Since I started from frags all I got now is bigger frags.

 

[VegasMike]

This is very interesting. Do you have the same table applying the Apogee correction factors?

I am starting to believe that the lightening of corals I experience is from a lack of light, not too much.

The gut reaction when corals lighten after being put into the tank is that the lights need to be turned down. I am starting to think just the opposite. I do not get tissue loss/burning at the tips, just an overall loss of color. Some SPS lighten where others do not. I have two tanks lit exactly the same. I have hammers/leathers at the top of one tank that are absolutely thriving while I have a brain on the sand that appears to be losing color and turning almost opaque. The second tank is mostly SPS and it is a mixed bag with some lightening and some doing great.

My settings are pretty low right now with the intent of moving them up a few % points each week. The lights are 10" above the water line and the tank is 30" deep.

DB 60
RB 50
W 35
UV 25
V 45
G 15
R 15

 

[VegasMike]

The Apogee correction factors are as follows:

Blue (10.7)
Green 5.8
Red 4.7
White (4.2)

I read this to translate that the Apogee reads blue 10.7 percent lower than it should, white 4.2 % lower, green 5.8% higher and red 4.7% higher, thus requiring the numbers above to be adjusted accordingly; Blues multiplied by 1.107, whites by 1.042, green by .942 and red by .953.

The shortfall is that there is no distinguishing between royal blue and deep blue. There is also no correction factor for UV or Violet. Given that the relative power of these is not great, any adjustment should not be that material. That being said, it would be wise not to make any such adjustment quickly.

The hard part is really the mix as it relates to PAR and how our corals respond. For example, quite a bit of the PAR is from the Blue LED's, over 50%. Is that what our corals experience in the wild? I really do not know.

I do know that getting into the 300-400 PAR range is not achieved by maintaining low power ratings across the board.

 

[Wazzel]

I do not have a corrected version of the table.

 

[VegasMike]

No problem, I used your table as a base, plugged in the correction factors and produced a new table. I used the blue correction factor on both DB and RB and no correction factor for UV and Violet.

I am not really sure variance of 10% is going to make a difference anyway as long as you are in the range.

Thanks for doing this.

 

[Wazzel]

Also, the meter does not pick up the entire spectrum of the light either. There is some dead band at the upper and lower ends.

 

[Wazzel]

I do know that getting into the 300-400 PAR range is not achieved by maintaining low power ratings across the board.

That was the idea that lead me to do the study and put together the power approximation spread sheet. The new LED fixtures were billed as approximately equal to 250 watt MH when they first came out. I made the assumption that was at full power and made it a point to get as much out of my unit as I could.