PAR Meter Readings

[DMBillies]

PAR Meter Readings (in Ã"šÃ‚µmol m-2 s-1)

Yesterday I played around with the club PAR meter a bit and I wanted to post up the results that I got in the interest of sharing and to spark some discussion. They were somewhat surprising to me, but Iââ"šÂ¬Ã¢"žÂ¢ll just present what I found and let the discussion go where it might.

Disclaimer: Iââ"šÂ¬Ã¢"žÂ¢m not a lighting expert. I havenââ"šÂ¬Ã¢"žÂ¢t checked these measurements against anything else. They seem to be very consistent within and between my tanks and ââ"šÂ¬Ã…"œbehaveââ"šÂ¬Ã‚ in the way I would expect for the most part (i.e., less PAR at greater depths). Take them for what they areââ"šÂ¬Ã‚¦ a valid attempt at being careful to get accurate measurements, but by no means a truly scientific treatment of the subject). Also, Iââ"šÂ¬Ã¢"žÂ¢m not trying to start a debate about what lights/ballasts/etc. are better.

Tanks:

90 Gallon (lights are 8ââ"šÂ¬Ã‚ from water)
---VHO run on an ARO
Phase 1 - Actinic - 2 x 48ââ"šÂ¬Ã‚ UV Lighting Super Actinic VHOââ"šÂ¬Ã¢"žÂ¢s (10 mos.)
---TEK Light Fixture
Phase 2 - Actinic/Day ââ"šÂ¬Ã¢â‚¬Å“ 1 x 48ââ"šÂ¬Ã‚ Geismann Actinic+ (13 mos.), 1 x 48ââ"šÂ¬Ã‚ Geismann Aquablue+ (11 mos.)
Phase 3 ââ"šÂ¬Ã¢â‚¬Å“ Daylight ââ"šÂ¬Ã¢â‚¬Å“ 2 x 48ââ"šÂ¬Ã‚ Current 10,000K T5ââ"šÂ¬Ã¢"žÂ¢s (1.5 mos.)

92 Gallon (lights are 10ââ"šÂ¬Ã‚ from water)
---Hellolights HO T5 Retros run on Advance - Centium electronic ballasts
Phase 1 ââ"šÂ¬Ã¢â‚¬Å“ Actinic ââ"šÂ¬Ã¢â‚¬Å“ 2 x 24ââ"šÂ¬Ã‚ UV Lighting Super Actinic T5ââ"šÂ¬Ã¢"žÂ¢s (2 mos.)
Phase 2 ââ"šÂ¬Ã¢â‚¬Å“ 2 x 24ââ"šÂ¬Ã‚ TRU 10,000K T5ââ"šÂ¬Ã¢"žÂ¢s (11 mos.)
Phase 3 ââ"šÂ¬Ã¢â‚¬Å“ 1 x 24ââ"šÂ¬Ã‚ TRU 10,000K T5 (11 mos.), 1 x 24ââ"šÂ¬Ã‚ UV Lighting 10,000K (3 mos.)

Nano (light is 4.5ââ"šÂ¬Ã‚ from water)
---150W JBJ K2 Viper (this was from the swap)
Coralife 20,000K (brand new)

Frag Tank (light is 3ââ"šÂ¬Ã‚ from water)
---Coralife Aqualight
Daylight - 96W 8,800K Customsealife, Actinic - 96W 460nm Current (I have no idea on the age of these because the light has had a number of ownersââ"šÂ¬Ã‚¦ I plan to replace when I order bulbs next)



Rather than post a bunch of numbers I thought I would make graphs. You should be able to get a pretty good idea of the actual numbers from the graphs if you are so inclined (or PM me for the actuals). These numbers are a little difficult to compare because each of the fixtures is a different height from the water and my set-ups are very varied. All measurements were taken directly below the center of the light fixtures or as close as I could get.

This first graph is the PAR readings for each of the tanks according to the distance of the meter below the surface of the water (so you would need to add the height above the water that the lights are mounted to get the total distance from the lights). My frag tank is very shallow, so the measurements stop at 5ââ"šÂ¬Ã‚.

 

[DMBillies]

The second graph below shows dry measurements from at or above the surface of the water. I couldnââ"šÂ¬Ã¢"žÂ¢t come up with a good way to standardize this distance and still hold the meter even, so for the most part this is the surface of the water. If you compare these numbers with the some of the numbers just below the water surface, youââ"šÂ¬Ã¢"žÂ¢ll see that the surface of the water creates a huge reduction in the amount of light that penetrates the water (on the order of 100 PAR or so). It is likely because of this huge reflection that I was able to see a +7 jump in par on most of my 90 gallon measurements just by shutting the cabinet door.

This last graph is just a graph of measurements from my 90 gallon tank. It shows the drop off in light output with the depth of the tank. Each of the lines tells what kind of light is on (actinics only, actinics with phase 2, and then all of the lights on). You can clearly see from this graph that the daylight bulbs have much more PAR and that the warmer (more red) wavelengths of light do not penetrate nearly as well to the bottom of the tank. These measurements are based on the distance from the surface of the water and the fixture is 8ââ"šÂ¬Ã‚ above the water.

Finally, I just wanted to say that the distance that the fixtures were above the water seemed to make a bigger difference than the ââ"šÂ¬Ã…"œtypeââ"šÂ¬Ã‚ of light. For instance, despite the fact that PCââ"šÂ¬Ã¢"žÂ¢s are generally considered not the best lights, they are putting out a very high amount of PAR just below the surface of the water. They are of course mounted the closest to the water of all of the lights and probably have the ââ"šÂ¬Ã…"œwarmestââ"šÂ¬Ã‚ color spectrum. For reference, I am able to move the Viper light up and down, so I tried it to see what it would do to my PAR readings in tank. With the fixture 4.5ââ"šÂ¬Ã‚ above the water and the meter 5ââ"šÂ¬Ã‚ below the water, I got a PAR reading of 130. When I moved the fixture up to 9.5ââ"šÂ¬Ã‚ above the water (leaving the meter in the same place), the PAR was reduced by almost half to 70. If these same outcome replicate with other tanks/situations, it seems like the distance of the fixture to the water may make a bigger difference in the amount of light getting into the tank than anything having to do with the type of light youââ"šÂ¬Ã¢"žÂ¢re using.