Daily Light Integral, PAR, and Photosaturation Discussion

zachxlutz

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I'd like to start a discussion based on a few things I've been reading lately regarding optimum daily light integral, PAR and photosaturation in our reef tanks and with the advent of this new lighting forum.

For those of you with PAR meters and the ability to continually monitor PAR via an APEX, or otherwise, what sort of DLI values are you targeting? How did you come up with your optimal DLI?

I'm hoping to learn about achieving optimal photosaturation, the effects of increasing PAR and decreasing the photoperiod as well as decreasing PAR and increasing the photoperiod.

How do nutrient levels, alkalinity and flow impact your choice of DLI?

DLI is calculated by multiplying the instantaneous PAR values (the number of photons falling upon 1 square meter per second, reported as µmol·m²·sec) by the number of seconds in the photoperiod and dividing by 1,000,000 to arrive at mol·m²·photoperiod. (Source: article linked below)

If PAR reads 350 and there is 7 hours of full lighting would the formula be (350*(3600*7))/1,000,000? This gives a DLI of 8.82. I'm unsure if this is optimal but I think it's close to what I'm working with in my system with it's current setup.

I've read @Dana Riddle's article here: http://www.advancedaquarist.com/2013/12/lighting but it's lengthy and quite a bit over my head! Has anyone poured over that data and simplified it a bit for us common folks?

So... Discuss!
 
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Dana Riddle

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These comments remind me of the very first MACNA I attended back in the mid-90's. I was trying to get down a crowded hallway towards the mens' room. My arrival was delayed by a number of people stopping me, saying something like "I've got a quick question...;)" You've got the DLI concept down pat and your calculation is correct. Although the DLIs I measured in Hawaii tidepools were substantially higher, you, again, are correct that photosaturation should be considered. Most corals' photosynthesis will be redlined (or very close) at a PAR value of 350. We know that alkalinity (acting as a carbon source for photosynthesis) can affect the rate of photosynthesis. Ditto for water motion (specifically velocity.) While there is any doubt that nutrient concentrations can influence the total amount of photosynthesis, I'm not aware of any testing done in closed systems (using PAM fluorometry or respirometry.) Sounds like a project when the new lab is up and going. In the meantime, I hope others will chime in. We've got a lot to learn.
 

GoVols

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These comments remind me of the very first MACNA I attended back in the mid-90's. I was trying to get down a crowded hallway towards the mens' room. My arrival was delayed by a number of people stopping me, saying something like "I've got a quick question...;)" You've got the DLI concept down pat and your calculation is correct. Although the DLIs I measured in Hawaii tidepools were substantially higher, you, again, are correct that photosaturation should be considered. Most corals' photosynthesis will be redlined (or very close) at a PAR value of 350. We know that alkalinity (acting as a carbon source for photosynthesis) can affect the rate of photosynthesis. Ditto for water motion (specifically velocity.) While there is any doubt that nutrient concentrations can influence the total amount of photosynthesis, I'm not aware of any testing done in closed systems (using PAM fluorometry or respirometry.) Sounds like a project when the new lab is up and going. In the meantime, I hope others will chime in. We've got a lot to learn.
Great post!!!!!!
Are you setting up a new closed system lab?

Regards, GoVols
 

Dana Riddle

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Yes. Most of the equipment has been unpacked after an epic move from Hawaii to Georgia. The new lab will be about 3x the size of the one in Kona and I look forward to getting my hands on some of the super corals I've seen in local shops!
 
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While there is any doubt that nutrient concentrations can influence the total amount of photosynthesis, I'm not aware of any testing done in closed systems (using PAM fluorometry or respirometry.) Sounds like a project when the new lab is up and going. In the meantime, I hope others will chime in. We've got a lot to learn.

The closest I've seen is an article by Eva Volman (1), Tim Wijgerde (2), Ronald Osinga (1,3) 'Corals as the ultimate vegans? However, this was more of an 'all, or nothing' experiment to determine if a Seriatopora coral that was fed as well as received light would do better than one that just received light alone. Would indeed be interesting to determine the level/freqeuncy of external nutrition required by a coral to achieve optimal photosyntheses.

And welcome back to the mainland :)

Ralph -
 

Dana Riddle

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Thanks for the 'vegan' reference. I saw Tim's work and found it interesting but would like to investigate further. My lab has all the equipment they used plus the fluorometer and chlorophyll meter. I don't expect the results to be earth shattering, but perhaps an important piece to the puzzle. But who knows (if I did, I wouldn't do the experiment! :D)
 
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zachxlutz

zachxlutz

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@zachxlutz
Do you want it broke down in "Layman Terms"?

Not necessarily layman terms, just trying to open up a discussion to hear about people's experiences with DLI, etc. Although, layman terms aren't so bad sometimes!

These comments remind me of the very first MACNA I attended back in the mid-90's. I was trying to get down a crowded hallway towards the mens' room. My arrival was delayed by a number of people stopping me, saying something like "I've got a quick question...;)" You've got the DLI concept down pat and your calculation is correct. Although the DLIs I measured in Hawaii tidepools were substantially higher, you, again, are correct that photosaturation should be considered. Most corals' photosynthesis will be redlined (or very close) at a PAR value of 350. We know that alkalinity (acting as a carbon source for photosynthesis) can affect the rate of photosynthesis. Ditto for water motion (specifically velocity.) While there is any doubt that nutrient concentrations can influence the total amount of photosynthesis, I'm not aware of any testing done in closed systems (using PAM fluorometry or respirometry.) Sounds like a project when the new lab is up and going. In the meantime, I hope others will chime in. We've got a lot to learn.

JUST A QUICK QUESTION! PLEASE EXPLAIN QUANTUM MECHANICS! lol

I'm excited to see folks post about their DLI numbers and what sort of success they are having.

Would you mind going into a bit more detail on water motion? Specifically, velocity? How does that apply to total GPH measurements vs. random flow patterns, etc?

Yes. Most of the equipment has been unpacked after an epic move from Hawaii to Georgia. The new lab will be about 3x the size of the one in Kona and I look forward to getting my hands on some of the super corals I've seen in local shops!

Where in Georgia are you located? We do have some great shops here! I'm in Lawrenceville.
 

GoVols

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Not necessarily layman terms, just trying to open up a discussion to hear about people's experiences with DLI, etc. Although, layman terms aren't so bad sometimes
lol,
I need "Laymen" or for @saltyfilmfolks to translate. :D

Just a simple guy it Tennessee. :)
 

saltyfilmfolks

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lol,
I need "Laymen" or for @saltyfilmfolks to translate. :D

Just a simple guy it Tennessee. :)
Ummm, ok. Ill give it a go.;Clown
Par is how much(P.A.R)" light" the coral is receiving right this second. DLI is how much it receives all day, or, during the photoperiod as it applies to our tank.

Lets reference the article.http://www.advancedaquarist.com/2009/5/aafeature
"DLI is important since it allows us to mathematically determine the total amount of radiation falling on a particular object (such as a coral), which then can be manipulated to arrive at other datum (such as an average amount of light)."

So lets say we have an acro(nothing fancy;Greedy), @ 250 par at the top of the tank.

"The formula for DLI is simple.(LOL) It is Photosynthetically Active Radiation (PAR, reported as micromole per square meter per second, or molm²sec) times the photoperiod in seconds.

For example, let's determine the DLI for a coral receiving 250 molm²sec for 12 hours:

250 molm2sec * (12 hours * 60 minutes per hour * 60 seconds per minute, for a total of 43,200 seconds) = 10,800,000 molm² in 12 hours. We can divide the result by 1,000,000 to arrive at usable shorthand of Mol per Day, which is 10.8 Mol per Day."

Thats great! My $$ Acro is now getting 10.8 Mol per day. K what do you do with that number?

"These DLIs are useless without a reference point. What is the DLI of sunlight falling upon a location with real coral reefs (such as the Big Island of Hawaii)? Unless you wish to sit in the baking sun taking PAR measurements every couple of minutes all day long, the task seems impossible (or at least most tedious and extremely boring). "

Ooh well that does get complicated. I dont know if anyone(JF?) has sat under the water where they aquacultured my $$ to see how mow many Mol it took make it so drop dead gorgeous.
Hmm. ok well lets assume it was under 15-20 feet of water and estimate its Dli Based on this.
"


Once data were downloaded and analyzed, these were the results:

  • 'Air' DLI: 41 Mol photons/Day
  • 'Reef' DLI: 30 Mol photons/Day "
It actually, if you consider the difference in depth, seems roughly to fit into the 10.8 Mol per day! Sweet! Clearly I am on the right track. Im buying more $$ coral.
umm, I only have a spot where it gets 390 par.:eek:

This I think is the difficulty in using DLI in the same way we measure Par, or alk or nutrient levels. Its much more like Alk in a way as it whats being used, but the specific number varies by the specific position of the coral in the tank. So to use it similarly to par in a deep reef tank just doesn't work.

BUT, it does need to be considered, and we do. We just call it our photoperiod. Now, with Leds timing and ramping its our "peak photoperiod".

How did you come up with your optimal DLI?
I wing it.;Stig

Ive chosen a par range in my tank I want to work in for the animals I want to keep. I know basically what I'm getting where from the top to the bottom AT PEAK.
Then I decided on when I want to look at the tank.(all day:D)

So now understanding that PAR is "cumulative" and that my photo period will be long, I set a shorter peak time with a slightly lower peak PAR, Knowing this would or could be easily changed if I ran into trouble.
For ease I drew a straight line from zero to peak over the time I wanted to run.

I work in film and television so Im pretty well versed in ratios of light and how easily the eye is fooled by amounts of light and what it takes to be able to see in the tank.

So when I ran the program it was actually too bright, both by eye and on my FC/Lux meter. So I knew it as going to be too much par over that time period(DLI) as well. SO i added a longer slower intensity ramp to the first ramp up and second ramp down. So now my first two and a half hours and last two and a half hours have less light than most people have in their bathrooms. The last 40 min in my 55 is honestly barely enough to see, but the corals close up slowly and the Ruby reds like to spawn then too.;Woot

SO even though many don't believe in Par and lux conversions, this is why I recommend folks with a par meter and led invest in a $15 lux meter. Its fun, I think it really adds enjoyment to the tank experience.

I have run into problems with coral greening from too much light, I just shortened the time and the intensity of the peak, once I set the ramps a year or more ago I haven't changed it.

Its exactly the same way many folks, regardless of the type of light, find their sweet spot. We all have too many types of coral with different lighting needs to consider an absolute number with DLI, but its the basis of how we decide on what works and find the right compromise. IMO, and correct me if I'm wrong.

My lights btwn run from 630 am and are off at 10pm, with a six hour peak.
 
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GoVols

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@Dana Riddle
Can you make a "Sticky" page at the top of your forum? With "lighting terms" like...

DLI = How much light a coral receives all day long

And so on.

Regards, GoVols
 

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While I don't have the ability to data log over the full course of the day with my current LED array , I can say that in my previous LED setup (no ramp up/ramp down feature) I had a DLI of 7.5. I now use a relatively short 'peak' of 3.5 hours (all channels on highest programmed settings) which is enough to stimulate excellent pigmentation of medium light stony corals such as Seriatopora, Pavona, Montipora 'Sunset' and Setosa with PAR ranging from 300 to 160. The rest of the 10 hr. daylight cycle is 'ramp up/ramp down'.

The control provided by an LED with a decent controller allows for some great fine-tuning. For this exmple, 3-1/2 hours peak allows for coloration and longer ramp times keep growth at a slower pace (small, mature tank). Using a shorter peak time also saves on the electric bill :)
 

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Nano sapiens

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thank you!

fwiw most will call a setosa med and low light:rolleyes:

True enough, but I found setosa to be highly photoadaptable. I've kept it at anywhere from ~120 - 320 PAR and various lighting spectrums and it still grows well within this range (although it's growth form will change dramatically depending on the intensity). Coloration is richest for mine at the higher PAR levels (photos below at ~310 PAR):



 
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zachxlutz

zachxlutz

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Wow! Lots of great info here already, let's keep it going!

@Nano sapiens Your tank is stunning! That polyp extension and coloration/fluorescence on that M setosa is outrageous!

While I don't have the ability to data log over the full course of the day with my current LED array , I can say that in my previous LED setup (no ramp up/ramp down feature) I had a DLI of 7.5. I now use a relatively short 'peak' of 3.5 hours (all channels on highest programmed settings) which is enough to stimulate excellent pigmentation of medium light stony corals such as Seriatopora, Pavona, Montipora 'Sunset' and Setosa with PAR ranging from 300 to 160. The rest of the 10 hr. daylight cycle is 'ramp up/ramp down'.

The control provided by an LED with a decent controller allows for some great fine-tuning. For this exmple, 3-1/2 hours peak allows for coloration and longer ramp times keep growth at a slower pace (small, mature tank). Using a shorter peak time also saves on the electric bill :)

I'd be curious to see what your DLI is with the short "peak" and the long ramps.
 

Nano sapiens

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@Nano sapiens Your tank is stunning! That polyp extension and coloration/fluorescence on that M setosa is outrageous!

I'd be curious to see what your DLI is with the short "peak" and the long ramps.

Thank you. I've had that Setosa in this little tank for nearly 9 years.

Totally unscientific, but I suspect the DLI is currently in ~ 5 - 6 range. I've actually had to start shortening my photoperiod a bit since the system is very nearly at 100% saturated Kalkwasser (I don't want to start with adding vinegar to the KW or using an additional 2-part), so it's now 9-1/2 hours for the daylight period and 3 hours of 'peak' lighting.
 
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justingraham

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Ummm, ok. Ill give it a go.;Clown
Par is how much(P.A.R)" light" the coral is receiving right this second. DLI is how much it receives all day, or, during the photoperiod as it applies to our tank.

Lets reference the article.http://www.advancedaquarist.com/2009/5/aafeature
"DLI is important since it allows us to mathematically determine the total amount of radiation falling on a particular object (such as a coral), which then can be manipulated to arrive at other datum (such as an average amount of light)."

So lets say we have an acro(nothing fancy;Greedy), @ 250 par at the top of the tank.

"The formula for DLI is simple.(LOL) It is Photosynthetically Active Radiation (PAR, reported as micromole per square meter per second, or molm²sec) times the photoperiod in seconds.

For example, let's determine the DLI for a coral receiving 250 molm²sec for 12 hours:

250 molm2sec * (12 hours * 60 minutes per hour * 60 seconds per minute, for a total of 43,200 seconds) = 10,800,000 molm² in 12 hours. We can divide the result by 1,000,000 to arrive at usable shorthand of Mol per Day, which is 10.8 Mol per Day."

Thats great! My $$ Acro is now getting 10.8 Mol per day. K what do you do with that number?

"These DLIs are useless without a reference point. What is the DLI of sunlight falling upon a location with real coral reefs (such as the Big Island of Hawaii)? Unless you wish to sit in the baking sun taking PAR measurements every couple of minutes all day long, the task seems impossible (or at least most tedious and extremely boring). "

Ooh well that does get complicated. I dont know if anyone(JF?) has sat under the water where they aquacultured my $$ to see how mow many Mol it took make it so drop dead gorgeous.
Hmm. ok well lets assume it was under 15-20 feet of water and estimate its Dli Based on this.
"


Once data were downloaded and analyzed, these were the results:

  • 'Air' DLI: 41 Mol photons/Day
  • 'Reef' DLI: 30 Mol photons/Day "
It actually, if you consider the difference in depth, seems roughly to fit into the 10.8 Mol per day! Sweet! Clearly I am on the right track. Im buying more $$ coral.
umm, I only have a spot where it gets 390 par.:eek:

This I think is the difficulty in using DLI in the same way we measure Par, or alk or nutrient levels. Its much more like Alk in a way as it whats being used, but the specific number varies by the specific position of the coral in the tank. So to use it similarly to par in a deep reef tank just doesn't work.

BUT, it does need to be considered, and we do. We just call it our photoperiod. Now, with Leds timing and ramping its our "peak photoperiod".


I wing it.;Stig

Ive chosen a par range in my tank I want to work in for the animals I want to keep. I know basically what I'm getting where from the top to the bottom AT PEAK.
Then I decided on when I want to look at the tank.(all day:D)

So now understanding that PAR is "cumulative" and that my photo period will be long, I set a shorter peak time with a slightly lower peak PAR, Knowing this would or could be easily changed if I ran into trouble.
For ease I drew a straight line from zero to peak over the time I wanted to run.

I work in film and television so Im pretty well versed in ratios of light and how easily the eye is fooled by amounts of light and what it takes to be able to see in the tank.

So when I ran the program it was actually too bright, both by eye and on my FC/Lux meter. So I knew it as going to be too much par over that time period(DLI) as well. SO i added a longer slower intensity ramp to the first ramp up and second ramp down. So now my first two and a half hours and last two and a half hours have less light than most people have in their bathrooms. The last 40 min in my 55 is honestly barely enough to see, but the corals close up slowly and the Ruby reds like to spawn then too.;Woot

SO even though many don't believe in Par and lux conversions, this is why I recommend folks with a par meter and led invest in a $15 lux meter. Its fun, I think it really adds enjoyment to the tank experience.

I have run into problems with coral greening from too much light, I just shortened the time and the intensity of the peak, once I set the ramps a year or more ago I haven't changed it.

Its exactly the same way many folks, regardless of the type of light, find their sweet spot. We all have too many types of coral with different lighting needs to consider an absolute number with DLI, but its the basis of how we decide on what works and find the right compromise. IMO, and correct me if I'm wrong.

My lights btwn run from 630 am and are off at 10pm, with a six hour peak.
Thanks for this a lot to read and re read in here and help a lot as there is only what other successful people have done with time periods and lighting over there tank. I need a bigger calculator
 
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