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What is your Daily Light Integral?


jservedio

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While PAR values are useful, the Daily Lighting Integral (DLI) is much, much more useful when it comes to understanding how much light your corals are getting. To get the DLI, you basically multiply your PAR out over the course of the day. I want to know approximations of what people's DLIs are to get a sense of what kind of light people are giving their corals so others can come up with good lighting schedules.

 

For example, if I have a T5 fixture that has 2 blue bulbs that put out 120 PAR and 2 day bulbs that put out 150 PAR and have the blues on for 12 hours a day and the whites on for 8 hours a day, I would calculate it like this:

 

Blue: 120 * 12 * 60 * 60 = 5,184,000

White: 150 * 8 * 60 * 60 = 4,320,000

Total of 9,504,000 - which is divided by 1,000,000 to convert between uMol and Mol to get my DLI of 9.5 Mol/Day which correlates to a depth of between 6 and 8 meters, or 20 to 26 feet.

 

In nature depending on the season, most reefs receive a shallow water (about 3' deep) DLI of 15-30 Mol/Day (Hawaii) with an average of 28 Mol/Day (in Thailand). Also, since we know how much light attenuation there is at depth, we can calculate what "depth" our tank is at.

 

Daily Light Integral: http://www.advancedaquarist.com/2009/5/aafeature

Irradiance on Reefs: http://www.reefkeeping.com/issues/2002-09/atj/feature/

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I'll start with mine on my Radion Pro with Wide angle TIRs. I have a complex lighting schedule, so it is a little different to calculate but here it is:

 

390 PAR * 2 hr * 60 min * 60 sec = 2,808,000 uMol/m^2

280 PAR * 2 hr * 60 min * 60 sec = 2,016,000 uMol/m^2

190 PAR * 4 hr * 60 min * 60 sec = 2,736,000 uMol/m^2

110 PAR * 2 hr * 60 min * 60 sec = 792,000 uMol/m^2

35 PAR * 3 hr * 60 min * 60 sec = 378,000 uMol/m^2

 

Total = 8,730,000 uMol/m^2 - divided by 1,000,000 = 8.73 Mol/Day

 

Which means my DLI at the surface directly under the Radion is 8.73 Mol/Day which is around 31% of the total light received at the surface (in Thailand, 28 Mol/day) and correlates to 6-8m or 20-26' deep depending on the clarity of the water.

 

 

Before increasing the intensity of the light, I kept a fairly similar schedual but peaked around 280 PAR at the surface which came out to 5.62 Mol/Day, which was around 20% of the light at the surface on a reef and correlated to 9-13m or 30-43' deep.

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