Light ramping no benefit?

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Sure, but not all of it is bounced, the the light under water still goes up or down at dawn/dusk just like out of the water. It doesn't just pop on. Dawn/dusk may be faster on the equator, but it isn't instant, it still ramps up or down
Much is bounced off the surface at a low angle speeding up the light to dark sequence. I never said it was instant my wife said it was in Kenya as above. I read on land it goes from light to dark in 30 mins, I don't know how fast underwater on the reef that's why I asked.
 

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Much is bounced off the surface at a low angle speeding up the light to dark sequence. I never said it was instant my wife said it was in Kenya as above. I read on land it goes from light to dark in 30 mins, I don't know how fast underwater on the reef that's why I asked.
Taking into account the sun's angle of incidence, on the equator the sun must rise ~ 10 degrees before any appreciable amount of light starts to penetrate ocean waters:

http://reefkeeping.com/issues/2002-09/atj/feature/index.htm

"When the celestial and atmospheric effects are considered with reflectance, solar elevation has a significant effect on the amount of light penetrating the ocean surface. While sunrise will bring some light to the submarine organisms, the amount of light reaching the organisms will not be significant until the solar elevation is at least 10º or even higher."

Some napkin calculations and I get 40 minutes for the sun to get from 0 to 10 degrees (on the equator), so there's your underwater 'dark to light' time.

Interesting point here is that a natural reef on the equator actually receives more like 10.5 hours of actual light, even though the above water illuminated period is 12 hours. For those running 12 hours because it's 'natural', you can actually save some money and run 10 - 10.5 hours. And if you ramp up say 2 hours morning and evening, most corals will do fine with 3-4 hours of a programmed 'peak intensity'.

I have no data that specifically shows that ramping is beneficial, but also no data to say it isn't. I have run an 8 hour with 2 hour ramp up/2 hour ramp down and 2 hours 'peak' (all LED channels) schedule in a small mixed reef for 10+ years with good results. I wouldn't go any less than this, but just goes to show that corals are quite adaptable when it comes to lighting.
 
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Eric Miller

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I use Kessils 360 W, all blue first thing in the morning then ramp up to 65% then slowly ramp back down to blue again. more Natural!
 

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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 typles (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.
 

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Clam
Thanks for sharing. I hadn't seen that paper, but it confirms that Tridacna species other than derasa have extremely high Saturation Points.
 

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Thanks for sharing. I hadn't seen that paper, but it confirms that Tridacna species other than derasa have extremely high Saturation Points.
O/t but the thing that struck me is the statements due to clam excrement the zoo is never nutrient limited.
Don't know the zoo clade(s) they use or if they a high light adapted but the possibility of the micro- enviroment favoring what it can take is interesting.

The fact that T. maxina is pretty much an autotroph is also interesting. If I understand this right. Sorry my clam nowledge is very limited
 

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I only have shrooms, a few zoas, a frogspawn, and a small cluster of Duncans. I have a 2 hour ramp up and 2 hour down. My corals are all starting the closing up about an hour to hour and a half prior to my ramp down. Don't know if it matters, but they do start to prepare for night.
Same experience I have too. Also I have recently added a Ducan. For the first few weeks it was in LFS lightning schedule. Just as the LFS store would close it has recreated. Now it seems to be more or less dosing my tank’s schedule.
My take on it that corals do care about light and the amount of light available does have an effect.
 

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O/t but the thing that struck me is the statements due to clam excrement the zoo is never nutrient limited.
Don't know the zoo clade(s) they use or if they a high light adapted but the possibility of the micro- enviroment favoring what it can take is interesting.

The fact that T. maxina is pretty much an autotroph is also interesting. If I understand this right. Sorry my clam nowledge is very limited
Tridacna clams are known to contain Clade A and C1 zoox clades, among a smattering of others. C1 is a generalist clade, suggesting that the tolerance of high light is not the clade itself, but instead optical qualities of the mantle or zoox self-shading.
 

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I don’t know much about corals, but one morning I woke up early and was standing by my freshwater tank enjoying a cup of coffee, the lights came on abruptly and my favorite golf ball shaped pearl scale goldfish darted across the tank then just stopped breathing and moving immediately. It was either a heart attack or stroke, I'm sure of it. I never saw it move that fast. Obesity may have been a cofactor, but it was definitely the shock of the light coming on that killed it.

Additionally, fish under water don’t experience sunrise and sunset the way we do. In the mornings and evenings, most light is reflected off the surface of the water due to the angle on incidence. (physics 101), so there is a big difference between the morning noon and evening light intensity in natural reefs. More so than on land. I have an Aqua knight V2 light on a 20gallon nano that has a 3 set point parabolic ram cycle feature built in. I have it set for 12 hrs from no light in the morning to full light at noon and low intensity actinic in the evening. No corals, but my BTAs seem much happier than the ones under another light that comes on and off abruptly.
 

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In my opinion, I think ramping the lights up and down would be beneficial to everything in the tank. I have 2 Kessil A80's on my son's 13.5g fluval with a controller. When the lights first come on, they are at their dimmist and all the way blue. They stay all the way blue for about 1 hour but the intensity goes up. After the first hour, the color temperature starts to move from extreme blue to more white or "natural looking" light with the intensity increasing to 100% by about mid day and stays that way for about 1.5 hours. Then the color temperature starts to swing back to all the way blue keeping 100% intensity till about 7-7:30 pm. Then the intensity fades to off by about 9-9:30 p.m. I like it. The corals in the tank seem to like it. I have monti, zoas, torch, and a duncan. I'm no expert. Just trying to replicate what a day is like for them to the best of my knowledge.
 

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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 typles (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.
Four pages of pretty much the same replies. Yes, fish may be startled by the instant on or off of lights (especially in a dark room with no extraneous light). But as most said, corals really don't care about ramping, they care about minimum and maximum intensity for photosynthesis.

Thank you @Dana Riddle your efforts here at R2R are greatly appreciated.
 
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Four pages of pretty much the same replies. Yes, fish may be startled by the instant on or off of lights (especially in a dark room with no extraneous light). But as most said, corals really don't care about ramping, they care about minimum and maximum intensity for photosynthesis.

Thank you @Dana Riddle your efforts here at R2R are greatly appreciated.
Agreed and you have justs added to the 4 pages lol, but really who cares.
 

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Four pages of pretty much the same replies. Yes, fish may be startled by the instant on or off of lights (especially in a dark room with no extraneous light). But as most said, corals really don't care about ramping, they care about minimum and maximum intensity for photosynthesis.

Thank you @Dana Riddle your efforts here at R2R are greatly appreciated.
Thank you!
 

Dana Riddle

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Has the question been answered?

While not necessary is there no benefit at all?
After giving the question more thought, the only benefit I can think of is when slowly ramped light intensity meets - and then exceeds - the Saturation Point and the Xanthophyll Cycle is activated. Generally, phycologists and botanists recommend 20 minutes to let various cycles of photosynthesis become fully effective when using a PAM fluorometer. But how much damage is potentially caused in this 20-minute period? On a natural level, many corals are exposed to sudden changes in light intensity (such as when a dark cloud that blocks sunlight moves out of the way.) It would be an interesting (and time consuming) endeavor to look at how photosynthesis is affected at fine scales (seconds as opposed to minutes.)
 

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I have not observed any notable benefits to my corals, though the fish behave differently at dusk .... which is pretty cool. I do think that the closer we can get to replicating the natural reef environment, unanticipated benefits may emerge. Coral spawning for example.
 

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I have not observed any notable benefits to my corals, though the fish behave differently at dusk .... which is pretty cool. I do think that the closer we can get to replicating the natural reef environment, unanticipated benefits may emerge. Coral spawning for example.
Re: Coral spawning and light. Onset of darkness is the biological clock for coral spawnings, in many cases. Some corals reproduce at random (the brooding Pocillopora damicornis, for example.)
 

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