PUR, PAS, PAR in Aquarium Reef/Planted Lighting

[Carl]

I have updated the PAR/PUR article from Aquarium/Pond Answers.
In particular the section dealing with PAR Compensation & Saturation points

Here is an excerpt:
PAR Saturation & Compensation Points of Acropora:

Acropora and other photosynthetic life require a minimum amount of light; this is called the "Compensation Point". The other lighting consideration is the "Saturation Point"; which is when the rate of photosynthesis does not increase with increasing light intensity.
For reef aquarium keepers, it is our goal to exceed the amount of light required for the Compensation Point but not pass the Saturation Point (it is noteworthy though, that the amount of light required for expression of color in corals often exceeds the Saturation Point).

Some species of Acrpora can change their "Compensation" and "Saturation Points" - this is known as Photoadaptation. Photoadaptation allows zooxanthellae to lower their Compensation and Saturation Points as depth increases (and available light decreases) and in shaded areas.
As we have already noted, a coral found in 40 meters of water sometimes requires less light than a coral found in a shallow tide pool. Photoadaptation is not unlimited, and some types of zooxanthellae can adapt better than others, and the type of zooxanthella plays an important role.

The graph below shows the PAR "Saturation Point" of various Acropora species



Carl

[Carl]

I've further updated the PUR, PAS, PAR in Aquarium Reef/Planted Lighting article

Here is an excerpt:
PAR stands for Photosynthetically Active Radiation.
This is commonly our starting point for determining whether or not a light fixture is adequate for our needs since it can be relatively objectively measured.
Further Reading: Aquarium Lighting; Measuring PAR

Before we go into depth about the meat of this article, we can use the basics of PAR combined with input wattage to get some useful information about the efficiency of an aquarium LED light (or really any aquarium light).
The reason this is important is that many if not most LED fixtures can keep high light planted or reef aquariums, but many if not most use a lot more energy and last much lower time due to inefficiencies than need be if built with efficiency and durability in mind (which bring up initial costs, but pays for itself long term).

Here are three examples using PAR reading directly under the lights:

* SB Reef Light PRO 32. This is rated at 363 watts input energy with a PAR of approximately 881 (100%) at 400mm of air.
This comes to .41 watts of input energy per 1 PAR

* Kessil A150. This is rated at 90 watts input energy with a PAR of approximately 325 (100%) at 400mm of air.
This comes to .27 watts of input energy per 1 PAR

* AquaRay Reef White NP 2000. This is rated at 30 watts input energy with a PAR of 380 at 400mm of air.
This comes to .08 watts of input energy per 1 PAR

* Finnex Planted 24/7 20 inch model. This is rated at 15 watts input energy with a PAR of 61 at 400mm of air.
This comes to .24 watts of input energy per 1 PAR

Obviously this is but a starting point as this article will clearly show in PUR & more, as we have to consider what we are using our lights for from planted freshwater to acropora reef lighting. But these efficiency readings speak volumes about who PUR, PWM, and wasted energy running fans affect PAR efficiency.
As per the LED themselves, different optics will also affect readings further out from the the center, which is why all are readings directly under the light.
However this certainly is an eye opening starting point as per the old term; "you get what you pay for" which when long term costs including short lives of popular "value" lights and 4-5 time operating costs in energy often these savings are evaporated after a few years.

Carl

[Carl]

I've further updated this important article that quite frankly stands alone in a cesspool of slick marketing where LEDs such as the "SB Reef Light", Kessil, or BML get huge fan bases only to fail or cease production a few years later.

www.aquarium-pond-answers.com/2012/03/pur-vs-par-in-aquarium-lighting.html

" Here area couple of excerpts:
"This article is to understand how we can achieve optimum lighting for growth of a photosynthetic organism in our planted freshwater & reef aquariums, while considering having a limited artificial energy source, like a aquarium light fixture. We know we cannot create the amount of useable light the Sun gives, so we try to optimize the light we are able to make for a given about of watts (input energy).

I should note that a lot of aquarium lighting use history has gone into this subject, as we already know based on use of "warm white" fluorescent shop lights in the 1970s that we can grow plants, just not as efficiently as the lights we have now (Advanced reef keeping was not even possible with the available lights then).
So for some aquarium lighting experts to dismiss subjects such as the concept PUR as "theory" I have to respectfully disagree and I would state that this is showing a lack of knowledge or experience of the history of aquarium lighting.

We know that many man made white sources will grow plants, how well depending upon the PAR at the level where the plants are located (PPFD) and the efficiency of the often limited light energy we can provide (PUR).
However, we also know based on aquarium lighting history that when tri-chromatic, actinic and other "tuned" spectrum light sources were employed, in other words PUR, we did a better job growing these plants and eventually photosynthetic corals, etc. with the same exact input wattages.
Example: 40 watt warm white versus a 40 watt Trichromatic or a 40 watt cool white versus a 20 watt trichromatic plus a 20 watt actinic for anemone aquariums.

BEWARE of a Parasite Resaler buying their way up in Google's algorithm using this information here and elsewhere to undercut professional sellers such as AAP to sell AquaRay LED lighting with an official sounding URL and offering promo codes for their clearance inventory!!! Once their inventory is gone, where will you be if you need warranty help?
Place their address into Google Maps and you will see it is not even a legitimate business!!
The sources above are from the ONLY true & experienced professional online resaler in North America, do not make the mistake of purchasing other than AAP""



Example for Kessil:
www.reef2reef.com/threads/kessil-failures.492684/