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Its a meter that you can use to measure the par output of the fixture at different levels
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Thoughts on RapidLED Onyx lights? I heard they compare to Radions?
. Lumens / Lux are also useless parameters as are related to human eye sensitivity (V lambda curve for who needs more details) and will show you couple of lux on a high power deep blue led. I would consider radiometric power in 400-500 nm interval as the main parameter. All other wavelengths (500-650) - greens, yellow, red, far red, lime and whatever other leds are on market are for visual appealing of tank only. Not influencing the corals.
. Easier.
. Hopefully the hobby market will mature someday and real pro lights will pop on shops.ive heared that if the kelvin of light gows higher than 14000k the corals do not survive more than 1 year for example 25000k[/QU
Had to repost as what I'm typing is part of Arman's quote for some reason
In my humble opinion, buying a LED fixture I would look for:
- brand and type of LEDs - we cannot dream to see flux / color bins on a fixture, but yeah, this would be more pricey. Those binnings are the main reason that not 2 lights are identical (even the same model of fixture can have 20-30% difference just thanks to unbinned LEDs). But also hate the "ultra efficient LEDs" slogan on some lights
- take the published power and consider only 75% of it in best case. All LEDs manufacturers websites publishes graphs and studies on which conditions have a light fixture to fulfill in order to be able to power a LED at 100% power. I have doubts that a small heatsink and a cheap fan can keep dozens of LEDs in a low enough temperature. As result the lifetime of LED drops (read intensity level in next few months) and in worst case color shifts. I would never power a led at more than 75% current without knowing lot of thermal details.
- leds to be clustered as close possible - to avoid ghosting / disco effects
- personally I consider collimators useless and prefer bare leds, as much wider / uniform spread. Someone will tell me that with collimators PAR values increase, etc. Agree, increase locally, right under the light. Keeping uncollimated LEDs I dont lost energy - everything is there, in the tank, everywhere. I can place corals everywhere in the tank, no risk to burn them, not risk to underfeed them.
- everybody admits that corals needs 400-500 nm spectral range to grow, with highest peak at 450 nm. Great. But then why PAR is an essential parameter?? PAR means radiometric power measured on 400-700 nm interval.
Having a lime/green/yellow light will show a huge PAR reading, but I will should not try it above a reef tank. Probably algaes will explode. Lumens / Lux are also useless parameters as are related to human eye sensitivity (V lambda curve for who needs more details) and will show you couple of lux on a high power deep blue led. I would consider radiometric power in 400-500 nm interval as the main parameter. All other wavelengths (500-650) - greens, yellow, red, far red, lime and whatever other leds are on market are for visual appealing of tank only. Not influencing the corals.
- safety features of the lights - what happens if the 2USD fan breaks? What if airflow is clogged? Will a thousand $ light just burn out?? Most probably components as fans have a much shorter lifetime than a well cooled/decently powered LED, so a nice way to replace it / clean it is essential.
And other details which convinced me in the end to not buy, but to build my own lights... If something goes wrong I can look into mirror, blame myself and repair/improve. Easier.
There are manufacturers of LED lights which provide books of details on the lights, including X-Rays for LEDs soldered on boards to prove that there are no micro air-bubbles in the solder to affect the thermal transfer... Sadly non of those guys plan to build reef lights. Hopefully the hobby market will mature someday and real pro lights will pop on shops.
I think you might enjoy this read at this lighting link: http://www.americanaquariumproducts.com/Aquarium_Lighting.html
Curious, Like what and why?Sorry, but I red it before and not agree with lots of things in there.

