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Discussion Starter · #1 ·
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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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
One theory is to go by daily light integral ( dli).

Dli = .0036 x par ( common usage, really ppfd) x light hours/day.
.0036 x 50 x 10/24 = .075
=
.0036 x 75 x 8/24
Roughly..
Or 16 hrs of 50 par = 8 hrs of 100 par.
And considered equivalent. .

So length of photoperiod is dependent on target dli.
Dli is dependent on plant err " needs" and ones ability to maintain adequate co2 and nutrients.

Of course that begs the question that a set par level needs to be defined on a "standard" photoperiod, which it is not currently afaict.
50 par for 6 or 8 or 10 or 12 hours are not equivalent in terms of dli.

Nor would going to extremes where one could break into photoinhibition. i.e 1000 par for 1 hr vs 100 for 10 hr. In some plants this can occur at relatively low par or dli

Next with ramping up/down the calculation of dli gets more difficult.

Then there is the "rest period" theory.
A "dark" photoperiod between 2 light ones so plants and nutrients can "recharge".
Complicating the def of a set photoperiod sort of. Some reef keepers even see saw hourly all day based on this premise though their base light levels are 2 to an order if magnitude different than the " usual" fw setup.

Nature itself is dynamic and hourly/ day/week/season par is inconsistent.
Of course that naturalness is usually detrimental to us where consistency is king
and we trained the plants to a certain schedule, including ramping ect.

Sooo after all that just adj either par or photoperiod to what your tank tells you is good. Not sure any of this really helps you
:)

Concepts above are fine. The math sucks.
Just use this calc
I need to see what went wrong above, besides old age and insomnia

[email protected] 12hr = [email protected] 8hrs = 2.16 moles/ meter sq day.


.0864 x ppfd x average photo period /24hrs
86400 seconds/day / 1000000 micromoles/ mole.
wikis wrong w/ 3.6 x 10 third:
 

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Discussion Starter · #3 · (Edited)
One theory is to go by daily light integral ( dli).

Dli = .0036 x par ( common usage, really ppfd) x light hours/day.
.0036 x 50 x 10/24 = .075
=
.0036 x 75 x 8/24
Roughly..
Or 16 hrs of 50 par = 8 hrs of 100 par.
And considered equivalent. .

So length of photoperiod is dependent on target dli.
Dli is dependent on plant err " needs" and ones ability to maintain adequate co2 and nutrients.

Of course that begs the question that a set par level needs to be defined on a "standard" photoperiod, which it is not currently afaict.
50 par for 6 or 8 or 10 or 12 hours are not equivalent in terms of dli.

Nor would going to extremes where one could break into photoinhibition. i.e 1000 par for 1 hr vs 100 for 10 hr. In some plants this can occur at relatively low par or dli

Next with ramping up/down the calculation of dli gets more difficult.

Then there is the "rest period" theory.
A "dark" photoperiod between 2 light ones so plants and nutrients can "recharge".
Complicating the def of a set photoperiod sort of. Some reef keepers even see saw hourly all day based on this premise though their base light levels are 2 to an order if magnitude different than the " usual" fw setup.

Nature itself is dynamic and hourly/ day/week/season par is inconsistent.
Of course that naturalness is usually detrimental to us where consistency is king
and we trained the plants to a certain schedule, including ramping ect.

Sooo after all that just adj either par or photoperiod to what your tank tells you is good. Not sure any of this really helps you
:)
JeffKrol

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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Discussion Starter · #5 · (Edited)
I may need to adjust my stance on this a bit..
What I gather from this:

Marginal yield drops as light intensity increases.

Then DLI can be equal for
an aquarium with higher par and shorter photoperiod
vs an aquarium with lower par and longer photoperiod.
however, DLI will be equal but DPI will be higher for the one with a longer photoperiod.

so basically, its more efficient to minimize light intensity while providing longer photoperiods?

I've read that medium light 40-60 micromoles PAR is usually set at 8-10 hours of light.
So for medium light plants, I should be using 40PAR at 10 hours or more?
If I had low light plants like Anubias, which could be at about 20-30PAR, I should provide 20PAR then just try to lengthen my hours?
Then high light red plants which need about 90+PAR should receive just 90 PAR, and again try to lengthen my hours?
 

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ATM I'm not sure about it really.
In the past my usual opinion was based on lengthening photoperiods for under- par - d lights so to speak to equal shorter periods of high par lights. But that was to increase dli really.
Thing is " now" it may be that when shooting for a high light dli using low light it is actually err " better" ????
Soo equal but not?



Like I had the right idea for the wrong reasons if that makes any sense.

As to pigmenting red plants... well high intensity was always the " go to" but now the question is high intensity for how long?
If one has the light capable of it a short ( hour?) burst of say 100par then cruise along at like 30-40 would add color while not stressing the the tank all day

Mimicking nature high intensities are of relatively short duration though natures relative low intensity isn' t always low so to speak .

Getting complicated and messy and just a thought exercise.

This study confirms that delivering the same DLI over longer photoperiods with lower PPFDs indeed results in greater DPIs in lettuce. Other studies have shown that longer photoperiods with lower PPFDs do translate into more growth.
 
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