Light intensity vs duration - The Planted Tank Forum
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post #1 of 18 (permalink) Old 05-03-2019, 02:58 AM Thread Starter
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Light intensity vs duration

I noticed something when looking at my shrimp tank that the random stem of Ludwigia Rubin I planted in there has a nice dark red color to it and the same plant in my high tech setup only gets red when grown tall.

I thought this was weird because my high tech gets about 70 par at the substrate and the shrimp tank gets about 30 par at the substrate. Other differences are co2 fert dosing and softer water in my high tech. I run the high tech 6 hours a day and the shrimp tank 15 hours a day.

Is this something talked about that I have missed? Achieving better coloring with lower light but at a long duration. Couldnít find much on it specifically during my search. Granted the plants in my high tech have better lusher growth but not as good of coloring.


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post #2 of 18 (permalink) Old 05-04-2019, 03:10 PM
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Stress pushes red in most plants .

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post #3 of 18 (permalink) Old 05-05-2019, 08:36 PM Thread Starter
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Quote:
Originally Posted by Aku Sakana View Post
Stress pushes red in most plants .

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Ok I can see that in the same way that high light causes the plants to use up a certain chlorophyll to make it red the longer duration is doing the same thing with lower par levels.

One plant I thought was funny was Ammania bonsai also is growing in this tank albeit slowly but still growing with very low light on a longer duration.

So it seems you can still get decent coloring and grow normally higher light plants in lower light as long as the duration is there. Iíll see how the other plants in the shrimp tank do with this method; s Repens, Ludwigia glandulosa. My other plants in there are known to grow in low tech already.


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post #4 of 18 (permalink) Old 05-16-2019, 01:37 AM Thread Starter
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So I trimmed the Ludwigia Rubin from my low tech shrimp tank and put it into my high tech and the color contrast is amusing
The red on the right is the Rubin and directly next to it to the left are the Rubin that has been in there. Planted the same day from the same source.

Redder at much lower par but for twice the duration.


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post #5 of 18 (permalink) Old 05-16-2019, 02:10 AM
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Will that's pretty interesting and I am not sure what to make of it. The color on the redder one is an odd color for Rubin. It's more of a muted red than I would expect to see.

How long has it been in the higher tech tank? If it's newer might just take more time. I would expect more red from those conditions. You sure about the 70 PAR?

FWIW, here it is under 110 PAR at the substrate for 8 hours a day. IME, high light brings out the best red. The extra light period might be making a difference, but I doubt it will get it's usual deep red under that PAR.



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post #6 of 18 (permalink) Old 05-16-2019, 04:13 AM
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What about actual spectrum of the 2 lights on the tanks in question?
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post #7 of 18 (permalink) Old 05-16-2019, 04:37 AM
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70x 6 = 420 cumulative PAR 17.5DLI
30 x 15 = 450 cumulative PAR 18.75DLI

your "low light" tank is brighter than your high light tank..

look up
Daily light integral..DLI
https://en.wikipedia.org/wiki/Daily_light_integral

granted not much of a "real" difference but ???
Quote:
Ok I can see that in the same way that high light causes the plants to use up a certain chlorophyll to make it red the longer duration is doing the same thing with lower par levels.
Err.. not really..
You can Nitrogen starve plants so that green chlorophyll is in short supply allowing the red pigments to "show" through..
so one possible reason would be the "low light" tank (not low light) has a shortage of nitrogen for chlorophyll production whereas the other has excess and a much healthier production of it.

spectrum related causes would be the low light tank has a lot more blue/violet/UV than the other.
Red pigments are produced as a "sunscreen" response to high energy photon excesses..
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post #8 of 18 (permalink) Old 05-16-2019, 02:47 PM Thread Starter
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So the shrimp tank the redder Rubin came from is a standard 10 gallon with a Finnex Stingray directly on the rim with glass top on for 12ish hours. Nitrate approximately 20ppm.

The higher tech is a 30Ē Finnex Planted+ about 15Ē off substrate and a 20 watt cfl 2700k the same distance horizontally mounted with a so so reflector. I dose 19.5ppm of kn03 per week and donít feed because there is only amanos in the tank.

Yeah I didnít figure I was right about the chlorophyll thing but was trying to understand.

This all had me wondering when I heard Cory from aquarium co-op mention light accumulation being the same regardless of high light low duration or low light longer duration. Just hadnít thought of that like that before. Didnít sound right when I heard it.


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post #9 of 18 (permalink) Old 05-16-2019, 03:29 PM
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Quote:
Originally Posted by jeffkrol View Post
70x 6 = 420 cumulative PAR 17.5DLI
30 x 15 = 450 cumulative PAR 18.75DLI

your "low light" tank is brighter than your high light tank..
Is that really true for aquarium application. So if I had a large deep tank and put 8 fixtures on top that housed very cheap lowest output LEDs, but they added up to more PAR then 2 fixtures that housed very strong LEDS it would give me more "light penetration" then the stronger LEDs?


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post #10 of 18 (permalink) Old 05-16-2019, 04:58 PM
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Originally Posted by Asteroid View Post
Is that really true for aquarium application.
AFAICT it's true for all photosynthetic organisms. Of course nothing is really that simple..
Since a lot of aquatics are classed "low light" plants the chances of light saturation increases..This might be somewaht eliminated at lower intensity longer duration lighting.
Of course that is sort of the opposite of what one expected..


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So if I had a large deep tank and put 8 fixtures on top that housed very cheap lowest output LEDs, but they added up to more PAR then 2 fixtures that housed very strong LEDS it would give me more "light penetration" then the stronger LEDs?
Generally speaking. The "high power" LED fixtures are usually lensed to concentrate the light. Also you have light attenuation through water (blue penetrates deeper than red) but that is sort of err very secondary.

100,000 lumen light pointed up and bounced off a ceiling will have probably low PAR value..
5000 lumens focused into a 2" spot will have Huge par ..in that 2" spot..

Power and geometry go hand in hand..

There is a Chinese brand of aquarium lights that use 90 degree reflectors and 1/2W emitters.. Need to find it. Would make a good comparison..

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post #11 of 18 (permalink) Old 05-16-2019, 05:28 PM
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Quote:
Originally Posted by jeffkrol View Post
Generally speaking. The "high power" LED fixtures are usually lensed to concentrate the light. Also you have light attenuation through water (blue penetrates deeper than red) but that is sort of err very secondary.

100,000 lumen light pointed up and bounced off a ceiling will have probably low PAR value..
5000 lumens focused into a 2" spot will have Huge par ..in that 2" spot..

Power and geometry go hand in hand..
Right, so for the application of growing plants in an aquarium the cumulative effect of more less powerful lights to increase PAR is kinda mute. The cumulative PAR will not be concentrated in the area where a plant that needs higher light would get it, compared to less fixtures with stronger bulbs and more directive light even though the PAR is less overall.


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post #12 of 18 (permalink) Old 05-16-2019, 05:44 PM
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Quote:
Originally Posted by Asteroid View Post
Right, so for the application of growing plants in an aquarium the cumulative effect of more less powerful lights to increase PAR is kinda mute. The cumulative PAR will not be concentrated in the area where a plant that needs higher light would get it, compared to less fixtures with stronger bulbs and more directive light even though the PAR is less overall.

PAR is measured in a spot at a time ..Measure any spot multiply by duration.. divide by 24..
Simplistic definition..technically need more than one spot (sq ft) and more than one measurement (most aquarium lights are still run err "consistent" ) which I now assume you were referring to..
Sort of like hot spots..

Point was looking overall though..

All difference factors have already been neutralized so to speak..


Cumulative effect always matters..

Take the same light.. dim it to 50%.. measure PAR DLI is different..1/2

https://gpnmag.com/article/daily-lig...egral-defined/

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post #13 of 18 (permalink) Old 05-16-2019, 05:51 PM
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I'm going by what you said here:

Quote:
Originally Posted by jeffkrol View Post
70x 6 = 420 cumulative PAR 17.5DLI
30 x 15 = 450 cumulative PAR 18.75DLI
How do you know that cumulative PAR is hitting that plant with that amount of light? I'm not doubting you, just trying for it to make sense to me in an aquarium application.


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post #14 of 18 (permalink) Old 05-16-2019, 05:57 PM
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Quote:
Originally Posted by Asteroid View Post
I'm going by what you said here:



How do you know that cumulative PAR is hitting that plant with that amount of light? I'm not doubting you, just trying for it to make sense to me in an aquarium application.
I'm not .. the whole point was to suggest that the low light high length photoperiod wasn't really that low in comparison.

Not to be an exact mapping of the entire tank..
A generalization. O/p needs to determine if it applies..





I know it sounded more specific than was meant.. but concept remains..
Instantaneous PAR measurements aren't the whole story..
Barring any dimming my "calculations" hold for that limited spot in those tanks...
o/p never stated if the measurement was near or far from any of the plants.. but if put near each, it's roughly valid..
If the lights aren't dimmed the change over time is minimal..

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post #15 of 18 (permalink) Old 05-16-2019, 07:48 PM
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NEED to clean up my mistakes by being to simplistic..
https://www.waveformlighting.com/hor...dli-calculator
70x 6 = 1.51 DLI
30 x 15 = 1.62 DLI

Concept I get...nuts and bolts not so much..

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