PAR Readings - Various Nano Lighting

[sammy33]

I have a series of PAR reading tests that I would like show the results of. These are real measurements of usable light intensity in various size aquariums with certain light setups. I have an Apogee Instruments Quantum Meter calibrated for electric light sources that reads PAR in µmol m-2 s-1. This meter has a submersible probe so I have taken all these measurements inside the aquariums I am testing...underwater. I feel that this type testing will give numbers that are useful on a hobby level and will be a good reference point for deciding on light systems for reef aquarium setups.

 

The top readings were taken just below the surface. All of the other readings were taken directly below the reflectors where possible. Most of the other readings show the depth where it was recorded and the number is shown at the relative position (left to right) where it was recorded. These readings are simply the PAR number the probe showed at that spot in the aquarium.

 

 

This is a 7g Mini Bow with a Sunpod 70w HQI fixture on the mounting legs. This was using the Ushio 70w 20K lamp which is shows higher PAR than the stock 14K Current USA lamp. Lamps about 5" off the water.

 

 

24g Nano Cube with a 150w HQI Sunpod. No glass cover, Current USA 14k stock lamp (less than 3 months old). Note the nano cube glass cover reduces these reading by about 15%. Bulbs 4" above water.

 

 

Custom 24g tank with 150w HQI Sundial w/ 2x32w dual actinic PC (214w total). 150w HQI lamp is 14,000K Ushio. Electronic ballast and all bulbs are less than 3 months old. Bulbs 6" above water.

 

 

This is a 30g Cube (Freshwater tank...I know!) with 2x36w compact fluorescent retrofit (72w total), WH5 ballast, reflectors with one 50/50 and one 6,700K bulb (bulbs over 1 year old). This is basically what the 24g Nano cube has. Bulbs 4" above water.

 

 

At the far end of the low side and for comparison - This is a 15g with a standard fluorescent strip light that comes stock with most starter aquarium packages. 18w T8 tube AGA stock lamp (broad spectrum daylight). Bulbs 3" above water.

 

 

On the extreme high end for comparision - 125g SPS reef with three 250w Ocean Light Pendants. 14K Ushio HQI lamps are less than 3 months old. Ballasts over a year old. Two 110w VHO Actinic 6-12 months old and two 80w T5 Actinic Blue 3-6 months old. Bulbs 8" above water.

[sammy33]

What the heck is PAR anyway?

 

PAR

The expression Photosynthetically Active Radiation, often abbreviated PAR (sometimes shown as Photosynthetic Photon Flux (PPF)), designates the spectral range of solar light from 400 to 700 nanometers that is useful in the process of photosynthesis.

From Wikipedia

 

Direct sunlight has a PAR of around 1200 to 2000 with the lower values encountered in the winter months and much higher in the summer. Clear day in Atlanta around noon and the PAR in direct sun is ~1640.

 

So what is a good PAR range for a reef tank?

I have heard recommendations of 200 to 600 PAR from the bottom of the reef to the top of the reef (Tyree 1999) with this being an acceptable range for "low, medium and high" light corals.

 

Sprungs Coral Reference Guide shows lighting values in a scale from 1-10 (low to high). In Adam Blundell's Lighting Article he proposes using these values as PAR by multiplying by 100. The scale next to each coral in the book can then be used to reference a PAR value (range) it will likely do well under.

Here are some examples:

 

Green Star Polyp (Pachyclavularia)

Lighting

(Sprung value) 3-9

(PAR minimum) 300

(PAR average) 600

 

Frogspawn (Euphyllia)

Lighting

(Sprung value) 3-8

(PAR Minimum) 300

(PAR average) 550

 

Acropora (Acropora)

Lighting

(Sprung value) 4-10

(PAR Minimum) 400

(PAR average) 700

 

Check out this article:

How Much Light?! Analyses of Selected Shallow Water Invertebrates' Light Requirements

by Dana Riddle

 

The article shows PAR data for photosynthesis saturation points and photo inhibition points both from laboratory tests and also light readings from various locations on the worlds reefs. This shows a good reference range of PAR requirements.

 

Hope this helps.

[HecticDialectics]

Those PAR minimums are completely off on the gsp and frogspawn...

 

But great test data!

[evilc66]

The PAR numbers seem really high for 150W MH. 986 PAR on a 150W Current USA 14k bulb? I've read significantly less under 250W and 400W MH. While I appreciate the effort taken, the numbers seem a little skewed.

[sammy33]

Those PAR minimums are completely off on the gsp and frogspawn...

 

But great test data!

I agree that those PAR levels as proposed by Blundell and Sprung seem high for GSP. I also think the numbers for the acropora seem a wee bit low (based on my personal experience). I have had GSP adapt to and grow well under PC lights with far less light intensity.

 

 

The PAR numbers seem really high for 150W MH. 986 PAR on a 150W Current USA 14k bulb? I've read significantly less under 250W and 400W MH. While I appreciate the effort taken, the numbers seem a little skewed.

Not skewed in any way but simply what my meter showed in the aquarium at the point indicated. I would be interested in seeing other PAR test results if you have them available. I am using a Apogee Instruments QMSS-ELEC meter to take my measurements. What results are you comparing this to?

[evilc66]

I was using that same meter that I had borrowed from my LFS (where I tested the bulbs). I have my own now which is a dual calibration unit. From what I have read so far, the sunlight calibration is more accurate for MH and LED (which is what I'm using it for), but the amount of error wouldn't account for that wild of a swing in results. I'll see if I can get some more tests done to compare. My LFS runs 250W 20K XM SE bulbs in PFO reflectors. Not the greatest reflectors, but should be equal to some of the fixtures you listed in your tests.

 

I have also tested against my own 70W Astralux in my BC14, and I don't think I ever reached close to 400 PAR, and it's supposed to be one of the best bulbs going. I might be able to pull a reading at lunch.

[sammy33]

evilc - Thanks for the great discussion.

 

I consulted with Apogee, before I purchased my PAR meter, on what they thought I would get the most accuracy with. They said the electric calibrated meter would give me the least error and that it would be on the low side by 2%. They said the sun calibrated meter would read high by 6%. This chart from their website shows the error factors for each type meter and various light sources.

[sammy33]

Those PAR minimums are completely off on the gsp and frogspawn...

 

But great test data!

 

What PAR minimums do you think for GSP and Frogspawn? Using the 1-10 scale (100 to 1000 PPF).

[HecticDialectics]

What PAR minimums do you think for GSP and Frogspawn? Using the 1-10 scale (100 to 1000 PPF).

 

 

like a .5 and a .8? I mean, you can keep em satisfied under a good amount of PCs... not that more light would hurt, but def. no where near 300 PAR...

[Mr. Fosi]

I can't say anything about the #s but I like the pics. Very understandable.

 

I'll be tagging along for the meter/# discussion.

[OceanNano]

Can we get some T5 (only) numbers if possible? Thanks & Great Idea BTW

[sammy33]

Can we get some T5 (only) numbers if possible? Thanks & Great Idea BTW

 

Not any T5 nano reefs but I do have a couple larger examples.

 

72g with 5x54w T5, TEK reflectors, Actinic+, Aquablue, Midday, Pure Actinic, AquaBlue and 1x39w T5, TEK reflectors, Actinic+. All ballasts are Advance spec ballast. These are mounted in a fan cooled canopy about 5" off the water.

 

 

125g with 4 rows of 2x39w with a mix of TEK and Ice Cap reflectors (312w Total). The Geisemann bulbs and Advance ballasts are less than 3 months old. Actinic +, Midday, Aquablue, Pure Actinic. Fan cooled canopy with bulbs 5" above water.

[evilc66]

evilc - Thanks for the great discussion.

 

I consulted with Apogee, before I purchased my PAR meter, on what they thought I would get the most accuracy with. They said the electric calibrated meter would give me the least error and that it would be on the low side by 2%. They said the sun calibrated meter would read high by 6%. This chart from their website shows the error factors for each type meter and various light sources.

 

The reason I mentioned the sunlight calibration is that when Advanced Aquarist was doing their review on the PFO Solaris, they found that the sunlight calibration more closely followed the response curve of the other (considerably more expensive) PAR meter. While that was for LEDs, it also seemed to hold true on some of their MH tests unless I was reading things wrong.

 

The error correction chart that you posted earlier is probably not something to live by. The bulb types they list and the corrections for them, are probably at a much lower color temp than we are using. One thing that has been noted with the Apogee meter is that as the light has more blue, the error changes. The sunlight calibration seemed to deviate less at higher color temps.

 

Don't get me wrong, the meter you have is still usefull. The error that was observed is not enough to make the unit questionable in it's accuracy. It just makes it harder to compare the results from two different units. What will make the unit usefull is using it consistantly from tank to tank.

 

Like I said earlier though, even with electronic light calibration, it still wouldn't generate that big of an error. I just decided to hedge my bets and get the meter that can do both

 

I never ended up taking that reading yesterday. Maybe today at lunch if I get a chance. I'll do it on electronic light so it's apples to apples, somewhat.

[evilc66]

Well, I must appologize.

 

Turns out that the meter that I was using must have been faulty. We were getting some erratic readings when we were testing, but didn't realize that the numbers were that off.

 

After testing my 70W Astralux with my new PAR meter, the numbers that you posted started to make more sense. At approximately 6" from the bulb (4" from the water line) I am reading about 540 PAR.

 

Looks like I am going to have to recompile all my test data for my LEDs now

 

Again, sorry about before. I didn't realize I was working with faulty equipment.

[ccjung]

The biggest problem with the Apogee meter is its response curve in the 350-500nm range. At about 420nm, its only counting 50-60% of the photons.

 

This was troubling to me when we ran our own analysis with the Apogee QMSS, since I was getting higher par readings with PCs watt per watt than some of our HQI systems. And the results were even more dramatic when we put in 2 PCS of DAYLIGHT color (vs 2 x 5050s).

 

 

As a result, we ended up getting an Ocean Optics USB 4000+ spectrometer instead.

[evilc66]

I agree. This issue has been noted on other websites also. Unfortunately, this meter is the only one within the practical budget of most hobbyists.

[johnr2604]

Very good info Sammy. I would love to see some numbers on some retrofits. See you at MACNA

[ccjung]

What you could do is obtain 2 PAR readings. 1 with Daylight and 1 with Actinic. Double the Actinic PAR readings and add them to the Daylight readings for a more realistic sense of PAR.

 

When you run the meter with both colors on, you should notice it will be around 70-80% of the number you get above.

 

HTH

 

Chris

 

 

 

We'll have our Spectrometer at our Booth at MACNA. Feel free to bring anything by.

 

Chris

[Mr. Fosi]

We'll have our Spectrometer at our Booth at MACNA. Feel free to bring anything by.

 

But is it calibrated for absolute irradience?