# Photoperiod vs Intensity



## FishWorks (4 Dec 2021)

Hi All,

As I understand, intensity levels are as follows:
Low light is 20-30 micromols PAR,
Medium light is 40-60 micromols PAR,
High light is 90< micromols PAR.

My 2 questions are what the ideal photoperiods are at these levels.

Would the ideal photoperiod for all these be 8-10 hours?

Or would it be better to taper down the light duration when we ramp up the light intensity?
like say:
11 hours at low light,
9 hours at medium light,
7 hours at high light?

Thanks


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## PARAGUAY (4 Dec 2021)

My answer possibly doesnt help much but because most dont have access to a par meter its a question of observation. You dont mention  low energy or high CO2 set ups both have different approaches.Longer photoperiods favour low energy and intensity can be controlled by a controller  or raising the light and using floating plants. Co2 set ups even though itd high energy the advice seems to be gradually increase the photoperiod around 8 hours  usual.


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## FishWorks (5 Dec 2021)

PARAGUAY said:


> My answer possibly doesnt help much but because most dont have access to a par meter its a question of observation. You dont mention  low energy or high CO2 set ups both have different approaches.Longer photoperiods favour low energy and intensity can be controlled by a controller  or raising the light and using floating plants. Co2 set ups even though itd high energy the advice seems to be gradually increase the photoperiod around 8 hours  usual.



Paraguay,

Thanks for the response.

I was wondering if I used 8-10 hours for all the lighting levels I mentioned, then total PAR received per day would increase with intensity.
In contrast, there is also the idea that the relationships arent linear, where the highlight plants needs for PAR are much higher. Meaning, 50PAR at 9 hours is the same with 100PAR at 4.5 hours but highlight plants need more light, hence 7 hours would be more suitable for high light plants.

However, as you said, observe and adjust to what looks good.

My plan is to test with low light plants at 30PAR starting with 6 hours of light, when I see growth, I will increase to 8 hours, then try to get to 12 hours by increasing by 30 minute blocks every 4 weeks.

Then with high light plants at 90PAR, starting with 6 hours of light, when I see growth, Will increase to 7 hours, then try to get to 12 hours by increasing by 30 minute blocks every 4 weeks.

If the plants start closing up, I stop.
If I get algae, I stop and reduce the hours.


Thanks


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## Karmicnull (5 Dec 2021)

As a rule of thumb you are less likely to get algae if your plants are constrained by light intensity rather than CO2 or ferts. Low tech tanks have a lot less CO2 so much lower light intensity is used to make sure it remains the limiting factor rather than CO2. Once you've got the light intensity right you can gradually increase the photoperiod.


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## PARAGUAY (5 Dec 2021)

@FishWorks . Obviously you want to experiment with . Why not set up a journal or thread in lighting


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## MichaelJ (6 Dec 2021)

FishWorks said:


> Paraguay,
> 
> Thanks for the response.
> 
> ...



Hi @FishWorks  I am no expert on this PAR thing (for starters, hardly anyone around owns a PAR meter and can still be highly successful with their planted tanks), but I am pretty sure the general idea is that light intensity is driving the plants metabolic rate - analogous to the accelerator pedal in your car - High RPM requires more energy than low RPMs. When blasting your plants with higher light intensity your upping the metabolic rate of the plants thus the need for nutrients - primarily CO2 - CO2 that needs to be available right there and then when the photosynthesis is happening. If not available, your plants will suffer. I reckon this is why I can get away with 12 solid hours of lights over my densely planted low-tech tanks without any issues whatsoever... the light intensity is well adjusted to the low amount of CO2 - If I wanted to increase my light intensity I would have to increase the available CO2 first and foremost... Just shortening my photoperiod to say 8 hours wouldn't work.

Cheers,
Michael


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## jaypeecee (15 Feb 2022)

Hi @FishWorks & Everyone,

Interesting thread and one that I'd previously overlooked.

I was thinking about this subject earlier today having been reading the following:



			Balancing Lights, CO2 and Fertilization
		


The above article goes back almost thirty years. I was interested to read that "tropical plants require a tropical photoperiod for optimal growth". And, @Christel adopts this approach, if I remember rightly. As does @MichaelJ: 



MichaelJ said:


> I reckon this is why I can get away with 12 solid hours of lights over my densely planted low-tech tanks without any issues whatsoever... the light intensity is well adjusted to the low amount of CO2



I think many UKAPS members opt for 'bright' lighting and shorter photoperiod. It's unfortunate and frustrating that we can't easily quantify PAR. Would I be correct in thinking that a more typical photoperiod amidst UKAPS members is around eight hours?

JPC


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## jaypeecee (15 Feb 2022)

jaypeecee said:


> It's unfortunate and frustrating that we can't easily quantify PAR.



Hi Everyone,

Although we may not be able to measure PAR, we can resort to a compromise. There are apps for Android (and, no doubt iPhone) that will measure Lux (Lumens/m^2). OK, Lumens are for humans but, so be it - as I said, it's a compromise. I've just installed _Lux Light Meter (DoggoApps)_ on an old Android phone and it looks promising. So, rather than talk about dim, bright, very bright, we can now quote measurements in Lux. May I suggest measurements be taken 30cm away from the light source? If this proves unworkable, we can just abandon the idea.

JPC


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## FishWorks (15 Feb 2022)

jaypeecee said:


> Hi Everyone,
> 
> Although we may not be able to measure PAR, we can resort to a compromise. There are apps for Android (and, no doubt iPhone) that will measure Lux (Lumens/m^2). OK, Lumens are for humans but, so be it - as I said, it's a compromise. I've just installed _Lux Light Meter (DoggoApps)_ on an old Android phone and it looks promising. So, rather than talk about dim, bright, very bright, we can now quote measurements in Lux. May I suggest measurements be taken 30cm away from the light source? If this proves unworkable, we can just abandon the idea.
> 
> JPC


@JPC and everyone,

8-10 hours seems to be to popular photoperiod. I will try to get a PAR meter and will report back as well.


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## jaypeecee (15 Feb 2022)

FishWorks said:


> I will try to get a PAR meter and will report back as well.


Hi @FishWorks 

Do you own a PAR Meter? Which one do you have?

JPC


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## arcturus (15 Feb 2022)

jaypeecee said:


> Hi Everyone,
> 
> Although we may not be able to measure PAR, we can resort to a compromise. There are apps for Android (and, no doubt iPhone) that will measure Lux (Lumens/m^2). OK, Lumens are for humans but, so be it - as I said, it's a compromise. I've just installed _Lux Light Meter (DoggoApps)_ on an old Android phone and it looks promising. So, rather than talk about dim, bright, very bright, we can now quote measurements in Lux. May I suggest measurements be taken 30cm away from the light source? If this proves unworkable, we can just abandon the idea.



How are you measuring the light? I have a similar app for the iPhone (Photone) and the developers recommend placing a light diffuser on top of the front camera. This makes it harder to compare readings between different devices.


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## jaypeecee (15 Feb 2022)

arcturus said:


> How are you measuring the light? I have a similar app for the iPhone (Photone) and the developers recommend placing a light diffuser on top of the front camera. This makes it harder to compare readings between different devices.


Hi @arcturus 

I've played around with several light measurement apps for Android, including _Photone_. I quite like _Color Picker_ as it provides an RGB analysis and dominant wavelength in a spectral format.



arcturus said:


> placing a light diffuser on top of the front camera. This makes it harder to compare readings between different devices.


What's the rationale behind that?

JPC


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## arcturus (15 Feb 2022)

jaypeecee said:


> Hi @arcturus
> 
> I've played around with several light measurement apps for Android, including _Photone_. I quite like _Color Picker_ as it provides an RGB analysis and dominant wavelength in a spectral format.
> 
> What's the rationale behind that?


I can only quote the Photone developers on that...




They keep an <interesting blog> btw.


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