Any Real Benefit - Ramping LEDS

[Sump Crab]

Is there any benefit to our corals when we ramp up and ramp down our LED lights throughout the day? Is ramping only for the visual aesthetics of mimicking sunrise and set?

 

[Ron Reefman]

In the 10+ years that led fixtures have been around in the reefing hobby, I've never heard anybody talk about any advantages to doing sunrise/sunset with their light fixture.

Well, OK, one person felt the fish were startled when the lights came on bright right away. So the gradual ramp of led fixture didn't scare or shock his fish.

With that said, I love having a long sunrise and sunset in my DT. But I completely understand it's strictly for our viewing pleasure. So I do a 4 hour sunrise and a 5 hour sunset. Most of which is weak enough that zooxanthellae photosynthesis is unlikely except the last hour of sunrise and the first hour... or maybe the first 2 hours of sunset.

 

[Zach B]

There was a recent post with the same question and a lot of good info

Light ramping no benefit?

Does anybody know of any research article suggesting corals couldn't care less if lights are ramped up and down during the day I have read they dont many times but have never read any article giving any evidence of such. Thanks.

www.reef2reef.com

 

[piranhaman00]

Fish yes coral idk but probably yes. I ramp my Fowlr but T5 full blast or nothing corals

 

[Ron Reefman]

Here is what Dana Riddle said:
The short answer is 'no' - ramping is not necessary for corals. Now for the long answer. All plants, algae, zooxanthellae have a minimum light requirement called the Compensation Point (CP). The CP is when photosynthesis provides enough oxygen to meet the respiratory requirements of the organism. For zoox, and I'm making a general statement, the CP is less than 100 PAR, and often less than 50. If your ramped light intensity doesn't meet this requirement, your corals might as well be in total darkness. On the other hand, plants/algae/zoox also have a point where increased light intensity does not increase the rate of photosynthesis - this is called the Saturation Point (SP). Again, the SP point varies among types (clades) of zooxanthellae. The stony coral Montipora capitata has a SP at a PAR value of just over 100 (it will bleach/die) if light intensity is too intense. The SP of Tridacna derasa is extremely high (no SP at PAR of 600. Other research suggest no SP at 2,000 PAR.) Meeting the Saturation Point is OK. If we equate rate of photosynthesis with coral growth rates, meeting the SP means good growth rates, hence ramping to the SP is a good thing. Exceeding the SP causes natural protective mechanisms to kick in (the Xanthophyll Cycle) and, while not harmful, wastes energy and runs the power bill up needlessly. If light intensity is strong, as we see mid-morning to late afternoon, the rate of photosynthesis actually drops to protect the zoox/coral - this is called Dynamic Photoinhibition. The Xanthophyll Cycle offers limited protection. If light intensity exceeds the protective capabilities of the Xanthophyll Cycle, damage to zooxanthellae, and hence the coral can occur. This is called Chronic Photoinhibition and causes bleaching, stunted coral growth, etc.
Bottom line: Pay close attention to light intensity, whether ramping is employed, or not. When I was responsible for coral culture at the coral farm back in the late 90's, LEDs were those little red lights on the coffee pot, hence we used metal halides (which of course are basically on/off lights with only a few minutes ramping at start up.) Growth rates were acceptable - as a commercial venture, it was in our best interest to grow corals quickly. Fast forward to 2020. I now use LEDs and, yes, I ramp them, but only to showcase the corals' fluorescence for my viewing pleasure.