Photoperiod vs PUR

[Sushitheshiba]

I just had a random thought/question about lighting and please correct me if I’m wrong: Let’s say that your tank’s chemistry/flow and everything is on point. Will having a longer photoperiod of LEDs that don’t have the best PAR/PUR do the same as lights with high PAR/PUR lighting that is only on for a short amount of time? Example would be 6 or 8 hours of low PAR/PUR vs 4 or 5 hours of high PAR/PUR. Still new to the hobby and would like to care for more sps corals. Thanks in advance!

 

[saltyfilmfolks]

Par would be intensity. (Brightness)
Pur would be quality

A light with very poor PUR won't do well no matter how bright nor how long

A light with OK but not great pur will do better at higher intensity and slightly longer duration.

Yes are in essence correct.

With all lights , example a really good one w good pur , you can run higher par shorter time OR lower par longer time.
Again , you're correct.

But mostly , don't overthink it.
It gets complex. Low PUR can mean the light is missing some essential parts of the spectrum. So no matter how long you run it or how bright.
And an ok par light may not have ok pur.

You are definitely on the right track though.
(Don't tell Anyone else this but),
A light with very hIgh pur is not as visually bright (lux/par) as a light with bad pur .

So if you have an idea of the spectrum the light provides(pur estimate) , you can then decide
On how long to run it.

 

[oreo54]

I just had a random thought/question about lighting and please correct me if I’m wrong: Let’s say that your tank’s chemistry/flow and everything is on point. Will having a longer photoperiod of LEDs that don’t have the best PAR/PUR do the same as lights with high PAR/PUR lighting that is only on for a short amount of time? Example would be 6 or 8 hours of low PAR/PUR vs 4 or 5 hours of high PAR/PUR. Still new to the hobby and would like to care for more sps corals. Thanks in advance!

You are referring to DLI...........

Units

The daily light integral (DLI) is a function of photosynthetic light intensity and duration (day) and is usually expressed as moles of light (mol) per square meter (m−2) per day (d−1), or: mol·m−2·d−1.[1][2] In other words, DLI measures the number of photosynthetically active photons (photons in the PAR range) accumulated in a square meter over the course of a day.

DLI is usually calculated by measuring the Photosynthetic Photon Flux Density (PPFD) in μmol·m−2·s−1 (number of photons in the PAR range received in a square meter per second) as it changes throughout the day, and then using that to calculate total estimated number of photons in the PAR range received over a 24-hour period for a specific area. In other words, DLI describes the sum of the per second PPFD measurements during a 24-hour period.[3]

If PPF stays the same for the entire 24-hour period, DLI in mol m−2 d−1 can be estimated from the instantaneous PPF from the following equation: μmol m−2 s−1 multiplied by 86,400 (number of seconds in a day) and divided by 106 (number of μmol in a mol). Thus, 1 μmol m−2 s−1 = 0.0864 mol m−2 d−1 if light intensity stays the same for the entire 24 hour period.

Theoretically its just the gross amount of usable photons over a period of time sooooooo 1000000 over 8 hours is the same as 2000000 over 4..

Things breakdown over extremes of course..
Of course to implement it one would need to know the optimum DLI

 

[Sushitheshiba]

Thanks everyone! And thanks for merging the thread @saltyfilmfolks