Michael

This thread is a place for members who use the PAR meter to record their results, and compare to others information. I suggest you use the "quote" option to copy this form into your post and then fill in the blanks.

PAR DATA COLLECTION
10 October 2011

Please fill out this form as completely as possible. Use a new form for each aquarium. You can also submit the information on the DFWAPC forum on Aquatic Plant Central and it will be immediately available for everyone.

Aquarium size:
(gallons and dimensions)

Type of light fixture AND reflector:
(power compact, T5 NO, metal halide, mirror polish reflector, white paint, mylar, etc.)

Number of lamps, bulbs, or tubes, and wattage:
(examples: “2 T5 HO tubes, 24 w” or “1 metal halide 150 w”)

Age of lamps, bulbs, or tubes:

Other information:
(brand, color temperature, spectrum, etc.)

Distance from light fixture to substrate:

PAR VALUES MEASURED AT SUBSTRATE:
(Tip: you may want to measure PAR in several different locations. You can report multiple measurements, or calculate an average.)

Comments: (Are there other conditions affecting light levels? What types of plants do you grow? Was the meter easy to use? Were you surprised by the results?)


Thank You!

Michael

I will start with surprising data from one of my tanks.

See, that was easy!

Michael

I have added a request for information about the reflector. This makes a huge difference, and I forgot it in the first version.

Thanks!

Virc003

..

Virc003

PAR DATA COLLECTION
10 October 2011

Please fill out this form as completely as possible. Use a new form for each aquarium. You can also submit the information on the DFWAPC forum on Aquatic Plant Central and it will be immediately available for everyone.

Aquarium size 15 gallon Long, 24" x 12" x 12" tall
(gallons and dimensions)

Type of light fixture AND reflector Cheap clip on desk lamp with white paint as reflector
(power compact, T5 NO, metal halide, mirror polish reflector, white paint, mylar, etc.)

Number of lamps, bulbs, or tubes, and wattage 1 x 26 Watt spiral CFL
(examples: “2 T5 HO tubes, 24 w” or “1 metal halide 150 w”)

Age of lamps, bulbs, or tubes ~1 month

Other information GE, 6500 K
(brand, color temperature, spectrum, etc.)

Distance from light fixture to substrate 20” (8” above waterline)

PAR VALUES MEASURED AT SUBSTRATE: at substrate 14; just under water 49
(Tip: you may want to measure PAR in several different locations. You can report multiple measurements, or calculate an average.)

Comments This tank is a rimless with a vine growing from the hob across the back of the tank, so I have the fixture tilted to put light on the tank and vine. Less than optimum par values are expected at the substrate.
(Are there other conditions affecting light levels? What types of plants do you grow? Was the meter easy to use? Were you surprised by the results?)


Thank You!
..

Virc003

PAR DATA COLLECTION
10 October 2011

Please fill out this form as completely as possible. Use a new form for each aquarium. You can also submit the information on the DFWAPC forum on Aquatic Plant Central and it will be immediately available for everyone.

Aquarium size 40 gallon, 36" x 15" x 16" tall
(gallons and dimensions)

Type of light fixture AND reflector 1 x 36” T5 NO dual bulb with original reflector (mirror polish)
1 x 24” T5 NO dual bulb with original reflector (mirror polish)
(power compact, T5 NO, metal halide, mirror polish reflector, white paint, mylar, etc.)

Number of lamps, bulbs, or tubes, and wattage 1 x 36” 10,000K 21 Watts
1 x 36” 6,700K 21 Watts
1 x 24” 10,000K 14 Watts
1 x 24” 6,700K 14 Watts
(examples: “2 T5 HO tubes, 24 w” or “1 metal halide 150 w”)

Age of lamps, bulbs, or tubes Average ~ 1 month except the 24” 10,000K which might be 3 years old

Other information
(brand, color temperature, spectrum, etc.)

Distance from light fixture to substrate 13”

PAR VALUES MEASURED AT SUBSTRATE: I am having trouble keeping any color except green in my tank, so my testing focused on how much light my glass top filters out.

@ substrate
Measurements with both fixtures: w/ glass 83, w/o glass 97
Measurements with only 36" lamp: w/ glass 48, w/o glass 54
Measurements with only 24" lamp: w/ glass 42, w/o glass 44

@ top (~ 1-2" below water line)
Measurements with both fixtures: w/ glass 365, w/o glass *
Measurements with only 36" lamp: w/ glass 281, w/o glass 303
Measurements with only 24" lamp: w/ glass 240, w/o glass 247

As you can see there isn't too much of a difference with or without the glass.

(Tip: you may want to measure PAR in several different locations. You can report multiple measurements, or calculate an average.)

Comments lights were arranged for optimum par values. Background of tank is overgrown and would skew results.
(Are there other conditions affecting light levels? What types of plants do you grow? Was the meter easy to use? Were you surprised by the results?)


Thank You!

*at 1-2" below the surface, there was not enough room for both lights to illuminate the same area. Most of the light from each lamp, because of the reflectors, is aimed straight down and I was unable to aim both at the sensor simultaneously.

I, also, just for fun measured, in roughly 2-3" increments, the par value from the substrate to the surface without the glass top using only the 36" fiture. These values are listed below.

Just under surface of water: 255
183
118
75
56
@ substrate: 52
directly under the light without any water: 609

Furthermore, for further reference to real sunlight: at 3:00 pm this afternoon I measured the sun in open air, and the meter showed about 2,000! A few inches below the water's surface in my pond values were still as high as 1,000.

Something else to add, I noticed something interesting involving the front glass of the tank. It seemed as though the glass would
reflect light back into the tank. Meaning I measured higher par values as I moved the sensor closer to the glass. If someone would confirm this, I would appreciate it. I'm not entirely sure my reflector aims straight down, so it might have something to do with this as well.

Michael

Here is another tank at the low end of the light range. This time I used the "cut and paste" commands to copy the form, and deleted some redundant stuff.

PAR DATA COLLECTION

Aquarium size: 20 tall, 24" x 12" x 16"

Type of light fixture AND reflector: power compact, flimsy mylar reflector

Number of lamps, bulbs, or tubes, and wattage: 1 power compact, 65w

Age of lamps, bulbs, or tubes: 3 months

Other information: Coralife fixture and tube, 10,000K

Distance from light fixture to substrate: 20"

PAR VALUES MEASURED AT SUBSTRATE: 16

Comments: There is a very thick background of vallisneria which blocks some light. Using the old watts per gallon rule, this is high light (3.25 wpg!). Now I know why nothing will grow on the bottom of this tank except moss.

Michael

Some more outdoor pond measurements, taken last month at about noon:

Just above the surface--1,700
12" below the surface--1,200
24" below the surface--800

I think we may need to change our definition of "high light".

BTW, thanks to Virc003 for posting all his information. He is a new member, and only lives 3 blocks from me, so he borrowed the meter this afternoon.

Virc003

I forgot to add too that I checked an actinic bulb on my 40 just for kicks (so 13" to substrate). With the 36" fixture and the 10,000K bulb and an actinic bulb, I got a 36 on the par meter at the substrate.

brokefoot

I have been doing a lot of reading on PAR measurements lately and have seen more than one person make the same observation.

For the sake of consistency people should probably try to take readings close to the center of the tank away from the glass.