Lighting an Aquarium with PAR instead of Watts

[hsilive]

ok here we go i used to grow pot i dont know bout all these numbers and what not but here is my break down

hpsv and mh lights had 6 ft growable light spec
floresents only 3 to 6 inches
led i only used for clones and it streched the plants alot

you do need a full spectrum of lights to grow in fact dif specs will help plants grow in different ways such as in pot with veggie growth and flowering
i will expiement with my new fluval 12g tank for us i think water helps increase the usable light kinda like a tin can phone works with sound so for my 12 i will use stock lights plus about 60 watts soft white led and 30 of uv trust me uv does help maybe will kill some algae too ! this is a tall tank and thats part of why im going overkill and if it dont work i will get a high pressure sodium vapor and a metal holide and try that ! just hoping between the blues whites and uv i will have a good mix and maybe with those watts hit the bottom of the tank !!

[accordztech]

Hoppy, have you ever put together the data that we collected at the last meeting?

[bradlgt21]

So since the 4 bulb aquaticlife fixture is about 90 Par at 25" would it be safe to say the 2 bulb version would be about 45 par at 25"? Is this the fixture tested?

AquaticLife T5 HO Dual Lamp Light Fixtures

[jonathan]

I wonder if there is a way to convert a photography light meter reading to par...

[mcarroll]

A photography meter is probably reading in LUX. If so...

One answer is that "no" you can't convert from LUX to PAR with a standard conversion.

Another is that "yes" you can convert as long as you know the same bulb's PAR index. (I.e. someone else has taken both a PAR and LUX reading of the same bulb you are using and created a conversion factor from these measurements.)

There's a wide variety of "color profiles" in bulbs, and this can have a big impact on the actual PAR you calculate. Having said that, if you know for a fact that one of the index bulbs has a similar color profile to your bulb, then you can still get some idea of your PAR from the calculation.

If you search, I think Advanced Aquarist has some index values listed somewhere.

I'm using a LUX meter as well...I think it you're aware of how it works and the limits involved you can make due pretty well without worring about PAR. (OTOH, if you can borrow a PAR meter though...)

-Matt

[mcarroll]

Originally Posted by jabba

Tank: 55 gallon, 19 inch tall
Lights: 2x Hagen Power-Glo T5HO 18,000k, 2150 lumens, 233 lux
Light Distance: 24 inch

Ok from what I've read so far, I should be under 40 par. I couldn't find anyone with a par reader for me to measure so I was hoping anyone can confirm this? I was planning to move it up by 12 inches from the top but I'm afraid of losing too much par.

To the degree you are confident of your current numbers, a bit of math should give you a workable number for your hypothetical setup.

As your space between the light and water surface doubles, the light intensity will be only 1/4 of what it was. Going the other way, you can quadruple your intensity by reducing the light's distance to the water by 50%.

You could expect a commensurate quartering (or quadrupling) of your value at the tank bottom.

(Effects are considerably more complex and severe when the water depth changes.)

-Matt

[hsilive]

wow i feel left out

[Hoppy]

Originally Posted by accordztech

Hoppy, have you ever put together the data that we collected at the last meeting?

I did something with it, but I'm not sure what. I think I added some data for the LED light we tested. That was a long time ago

[Hoppy]

Originally Posted by bradlgt21

So since the 4 bulb aquaticlife fixture is about 90 Par at 25" would it be safe to say the 2 bulb version would be about 45 par at 25"? Is this the fixture tested?

AquaticLife T5 HO Dual Lamp Light Fixtures

That should be a good guess. I don't think I have any other data for Aquaticlife fixtures.

[Hoppy]

Originally Posted by mcarroll

A photography meter is probably reading in LUX. If so...

One answer is that "no" you can't convert from LUX to PAR with a standard conversion.

Another is that "yes" you can convert as long as you know the same bulb's PAR index. (I.e. someone else has taken both a PAR and LUX reading of the same bulb you are using and created a conversion factor from these measurements.)

There's a wide variety of "color profiles" in bulbs, and this can have a big impact on the actual PAR you calculate. Having said that, if you know for a fact that one of the index bulbs has a similar color profile to your bulb, then you can still get some idea of your PAR from the calculation.

If you search, I think Advanced Aquarist has some index values listed somewhere.

I'm using a LUX meter as well...I think it you're aware of how it works and the limits involved you can make due pretty well without worring about PAR. (OTOH, if you can borrow a PAR meter though...)

-Matt

As long as you are working only with fluorescent bulbs, with color temperatures between about 6500K and 10,000K, you can divide the lux reading by 76 and get reasonably close to the PAR value. Lights with more red or near UV in their spectrum can't be estimated with the same constant. The Lux meter is measuring a very small band of the spectrum compared to the PAR spectral range. (Sunlight also requires a different constant to convert from lux to PAR.)

[Yankee]

Hi I was looking at your LED chart and it says "Finnex Ray II DX". I can't find this fixture. Is this supposed to be the DS with 7000K LEDS? If so I think this is going to be a great option for me - at 24" this fixture is putting out high par ratings and is right in my budget.

[Hoppy]

Originally Posted by Yankee

Hi I was looking at your LED chart and it says "Finnex Ray II DX". I can't find this fixture. Is this supposed to be the DS with 7000K LEDS? If so I think this is going to be a great option for me - at 24" this fixture is putting out high par ratings and is right in my budget.

http://www.plantedtank.net/forums/sh...d.php?t=189944 is the most up to date data on Finnex lights.

[Yankee]

Originally Posted by Hoppy

http://www.plantedtank.net/forums/sh...d.php?t=189944 is the most up to date data on Finnex lights.

Thanks a lot, very informative! How up to date are the "high light" par parameters? I know the numbers are generally arbitrary but recently I've seen 80-120 par being labeled high. Would 50 par be capable of growing light demanding plants? I.e. dwarf baby tears.

[Hoppy]

Originally Posted by Yankee

Thanks a lot, very informative! How up to date are the "high light" par parameters? I know the numbers are generally arbitrary but recently I've seen 80-120 par being labeled high. Would 50 par be capable of growing light demanding plants? I.e. dwarf baby tears.

Because there is no widely accepted definition of "low", "medium" and "high" light, we can set our own definition if we want to. I like the idea that "low" means enough to grow many plants, and CO2 isn't at all necessary. "Medium" is enough to grow a very large variety of plants, with CO2 being highly recommended, and necessary for many of those plants, but the CO2 concentration doesn't need to be near the maximum the fish will tolerate. "High" is everything above "medium", and the CO2 concentration needs to be near the maximum the fish tolerate. (Plus, for both medium and, especially high light tank maintenance and setup need to be done very thoroughly and well to avoid algae problems.) Based on that I like 20-35 micromols of PAR as "low" light, 40-50 or 60 as "medium" light, and above that as "high" light. I don't have any argument with those who think different levels are more appropriate - they may be.

HC can be grown with 50-60 micromols of PAR as long as you use a good CO2 concentration too.

Remember, the PAR numbers are those at the substrate level in the middle portion of the tank. The actual PAR in the tank varies, being higher nearer to the water surface, lower in areas away from the middle portion of the tank and in shaded areas. The actual PAR at the plant leaves needed to grow a plant well is another subject.

[Yankee]

Originally Posted by Hoppy

Because there is no widely accepted definition of "low", "medium" and "high" light, we can set our own definition if we want to. I like the idea that "low" means enough to grow many plants, and CO2 isn't at all necessary. "Medium" is enough to grow a very large variety of plants, with CO2 being highly recommended, and necessary for many of those plants, but the CO2 concentration doesn't need to be near the maximum the fish will tolerate. "High" is everything above "medium", and the CO2 concentration needs to be near the maximum the fish tolerate. (Plus, for both medium and, especially high light tank maintenance and setup need to be done very thoroughly and well to avoid algae problems.) Based on that I like 20-35 micromols of PAR as "low" light, 40-50 or 60 as "medium" light, and above that as "high" light. I don't have any argument with those who think different levels are more appropriate - they may be.

HC can be grown with 50-60 micromols of PAR as long as you use a good CO2 concentration too.

Remember, the PAR numbers are those at the substrate level in the middle portion of the tank. The actual PAR in the tank varies, being higher nearer to the water surface, lower in areas away from the middle portion of the tank and in shaded areas. The actual PAR at the plant leaves needed to grow a plant well is another subject.

Great, thanks a lot! I'm thinking now I will run 2 2x54w aquatic life t5's to get me well over the recommendations. Thank you again, very informative article and recommendations.