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DLI (Daily Light Interval) and Why PAR Isn't Accurate

Cody

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I think that as a community, we need to move past PAR as a sufficient source of information of how to gauge the light needs of our corals. If I was telling you how to bake a a lasagna and I told you that it needs to be cooked at 350 degrees, then what would your next question be? Of course, it would be "how long?" Par is a measure of the amount of light, or radiation (hence the "R" in photo-synthetically active radiation) per second that are hitting a given surface area. As you will note while using the PAR meters that are a wonderful perk of being a supporting member of MARSH, there's a constantly changing number for your readings. This is due to the water surface, etc changing, but it's trying to give you the best quote of radiation per second. Again, what the meter is trying to do is to calculate how much light is hitting that meter per second. It's telling you the temperature in the oven. We also have to look at the longevity in which the lasagna, or our corals, are being cooked. DLI (Daily Light Interval) takes into consideration both parts of that recipe. The basic calculation is {(par*hours*minutes*seconds)/1000000}. At that point, we can all start making accurate comparisons.

Longer photo-periods with lower lights, and shorter-photo periods with higher lights can produce the same amount of radiation hitting the corals within a 24 hours period. At the end of the day, the coral received the same sum of radiation, but what differences can these different light schedules make? I'd have to find the article, but Ecotech seemed to find that the difference was coloration and algae growth. The higher intensity, shorter photo-period produced less algae. I'll look for that video tomorrow and link it. Anywho, I just wanted everyone to start thinking about this when you're using the MARSH par meters. Find your DLI. Report whats working for you in the DLI results and let's get more insight into how to cook these lasagnas.
 

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steveb

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@Cody you should be able to attach xls/xlsx/doc/docx now.
 
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Cody

Cody

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I see i'm not the only one who watched the new BRS video.
Following this thread!
I love their "investigates" videos but I haven't watched in a while. I started learning about this concept maybe six months ago and just got around to writing about it. Which video are you referring to?
 
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Cody

Cody

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@Cody you should be able to attach xls/xlsx/doc/docx now.
Thanks, Steve. I attached the spreadsheet to the original post. Yall check it out! Convert your last readings with the par meter and let me know your DLI!
 

DwPolcyn

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I love their "investigates" videos but I haven't watched in a while. I started learning about this concept maybe six months ago and just got around to writing about it. Which video are you referring to?
They just posted it yesterday
8-bulb T5 + led bars here (switching to G5 soon) but I got Total DLI 31.5
My two xr15s both have their plastic housings cracked from the torque screws being over tightened. Still waiting for an RMA from Ecotech
 
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Cody

Cody

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They just posted it yesterday

My two xr15s both have their plastic housings cracked from the torque screws being over tightened. Still waiting for an RMA from Ecotech
Hahaha oh lord. My timing is terrible. In all honesty, my post wasn’t inspired by their video. As quite a few members can attest to, I’ve been using my lasagna analogy for months now. Or at least, I’ve been yelling it at anyone who would listen haha
 

DwPolcyn

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Hahaha oh lord. My timing is terrible. In all honesty, my post wasn’t inspired by their video. As quite a few members can attest to, I’ve been using my lasagna analogy for months now. Or at least, I’ve been yelling it at anyone who would listen haha
Great minds think alike!
 

TX_Punisher

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They just posted it yesterday

My two xr15s both have their plastic housings cracked from the torque screws being over tightened. Still waiting for an RMA from Ecotech
I emailed them immediately after I received my 2 (still need 1 more) and sent them serial #'s and my info. BOOM, an hour later they replied telling me they were sending out 2 new face plates. I had them in 3 days.
 

DwPolcyn

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I emailed them immediately after I received my 2 (still need 1 more) and sent them serial #'s and my info. BOOM, an hour later they replied telling me they were sending out 2 new face plates. I had them in 3 days.
What!? I've been sitting on an unanswered email for over 2 weeks. I assumed it was the human malware, guess I'll resubmit my ticket.
 
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Cody

Cody

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8-bulb T5 + led bars here (switching to G5 soon) but I got Total DLI 31.5
Dang!!! I finally got a good par read and calculated mine out to about 14, but I’m looking to lower it. Some corals are looking pale and I believe that’s because they were getting hit with 550 par for seven hours straight. I’m going to lower mine near 10. I was reading a thread where someone mentioned that WWC and Jason Fox keep theirs around 10. Not sure how truthful that is, but my corals seem to be telling me might lights are too high.
 

TX_Punisher

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Unless I did it incorrectly, here's my lighting and schedule:

1--60" XHO actinic (9a-11:20a, 5:30-8:15p)
1--60" SB 50/50 actinic, UV (8:15-10:15a, 3p-10p)
2/8 60" T5 (blue plus) (9a-12p, 5:30-7:50p)
6/8 60" T5 (2bp, 2cp, 1 white, 1 p+) 11a-5:30p)

It's a bit hard to decipher it all with overlaps, and leds turning off and then back on. I did measure PAR toward top of rockwork (some sps there) with all lights on and it was 650+. I figured that was a bit much even though some stickheads in Houston run over 900, I dialed it back. Stuff is growing and coloring up so I'll be leaving it alone until I switch to the G5 Pros.
 
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Cody

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Unless I did it incorrectly, here's my lighting and schedule:

1--60" XHO actinic (9a-11:20a, 5:30-8:15p)
1--60" SB 50/50 actinic, UV (8:15-10:15a, 3p-10p)
2/8 60" T5 (blue plus) (9a-12p, 5:30-7:50p)
6/8 60" T5 (2bp, 2cp, 1 white, 1 p+) 11a-5:30p)

It's a bit hard to decipher it all with overlaps, and leds turning off and then back on. I did measure PAR toward top of rockwork (some sps there) with all lights on and it was 650+. I figured that was a bit much even though some stickheads in Houston run over 900, I dialed it back. Stuff is growing and coloring up so I'll be leaving it alone until I switch to the G5 Pros.
You’d need par reading in addition to these time schedules to calculate the DLI.
 

TooMuchDog

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Do you have some feeling for where the limits are? It would be interesting to see what you could get away with on the lower end of par just by running cheap lights for a 14 hour day or something like that. Cooking a lasagna for 14 hours at 70 degrees or for 5 minutes at 1000 degrees will product very different, equally terrible lasagnas
 

Stickboy97

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Why do you put your max PAR and not your average? I have a hot spot in the middle of my tank of about 600 PAR, up close to the surface, but no coral in that location. All of my coral start at least 6" below the surface & the readings there are pretty constant at 300 PAR.

At max 600 PAR I have a DLI of 16.2 but at the average 300 PAR I have a DLI of 8.1.
 
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Cody

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Why do you put your max PAR and not your average? I have a hot spot in the middle of my tank of about 600 PAR, up close to the surface, but no coral in that location. All of my coral start at least 6" below the surface & the readings there are pretty constant at 300 PAR.

At max 600 PAR I have a DLI of 16.2 but at the average 300 PAR I have a DLI of 8.1.
The calculator would be used for each location of par that you measured. For instance, if you took the measurements for 16 locations in your tank where corals are, the calculator would be used 16 times.
 
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