Photo period for LPS?

[BeachVacationer]

Assuming one has the proper lighting allowing for photosynthesis to operate at max capacity, is there a point where having the lights on longer is of no benefit to the corals?

I was shopping recently at a high end reef shop and was talking about lighting and photo periods. He said corals need only 5 to 6 hours of light per day. Beyond that there is no benefit for them. The only benefit is to the owner who can enjoy seeing the corals lit up in the tank. And that corals need periods of no light, so don't keep moon lights on overnight. I found that every interesting. Have you heard this too? If true, longer photo periods might just be promoting unwanted algae growth.

 

[Steve Atkins]

That might be close to the case.

In the tropics the days last 12 hours and sun sets and sun rises are quite abrupt. On top of that it will take a few hours for the sun to get high enough to penetrate with much force to any depth then later another few hours of diminishing light as the sun heads towards setting. So if you take 2 x 3 hours off your 12 hours you have 6 hours.

Steve

 

[Ron Reefman]

I can't tell you which marine biologist wrote the article, but that was pretty much what they said.

It takes a hour (more or less) of high enough PAR to get photosynthesis started and then it runs for 4 to 6 hours and shuts down. Leaving lights on longer does nothing for creating zooxanthellae food. It may have some beneficial affect on the work of the coral polyps in their job of growing or reproducing, but not in food production.

 

[Wazzel]

If you have enough PAR output then a few hours will be fine, if not then you need a longer duration. With all the variation in light system, aquarium depth, etc there is no one size fits all solution.

I use programmable LEDs. I run 14 hours total, 5 hour sun up/down ramps and 4 hours at peak intensity. It is working well for me.

 

[nuxx]

We run our lights pretty long, 12 hours full cycle.

Only really 6 hours of peak brightness.

Various hammers, torches, frogspawn, acans, etc... are thriving

 

[Perth_reefer]

A good analogy I heard is that the amount of light a coral needs is like catching rain in a bucket. If you have light rain (low PAR output lights) then it'll take the majority of the day to fill the bucket, heavy rain (High PAR output lights) and it might fill in a couple of hours.
As an example, the coral reefs of Hawaii are subjected to about 16Mol photons per day in Autumn, to achieve this you would have to run lights giving 450PAR just below the water surface for about 10 hours a day....this would be to mimic the output of the sun in Hawaii, if you've ever put a quantum meter out in the sun you'll know that we can not get close to replicating that kind of light in our homes, I measured 1860PAR at the just below the surface of the Indian Ocean on a winters day here last year, the difference being that generally our coral is a few 100mm from the surface water in our tanks, so light doesn't have to penetrate as far.
So it does help to know what levels the coral you keep are exposed to in the wild roughly, as a general rule of thumb Acropora photosynthesis occurs between 350 and 450 dependant on species. I have about 650PAR just below my water surface, which gives me about 430 at mid tank level, so for me:-

650(PAR) x 8(hours) x 60(minutes) x 60 (seconds) = 18'720'000 molm2

18'720'000(molm2) / 1'000'000 = 18.72Mol

18.72Mol is slightly above the recorded levels in Hawaii on an Autumn day (over 12 hours).

So there is definitely benefit to measuring PAR levels in your tank as well as knowing roughly what PAR levels your corals are exposed to in the wild.

 

[Ron Reefman]

kenpau, that is a very cool analogy, but I'm pretty sure it's not applicable.

You need to reach a base level of some PAR before the zooxanthellae will even try to start the process. There is a period of time used to clear oxygen or CO2 or something like that before photosynthesis will even start. Once the process starts, it's going and adding more PAR doesn't make the process run any faster. And if the level of PAR goes down the process shuts off.

I'll admit it was a few years ago that I read the article, so I'm a bit fuzzy on the details. The part I wanted to know was how long the process would run. Most coral's zooxanthellae only do photosynthesis for 4 to 6 hours no matter how much more light you add after the process has started. And adding more light didn't produce more end product.

 

[Scorpius]

I'm currently running my lights 11 hrs with 3 hrs peak intensity. I'm slowly ramping all my numbers up and watching for coral reactions.

 

[Ron Reefman]

kenpaw, I'll ask you to accept my humble apology. I did some more research and it appears that intensity does make a difference. I stand corrected. In fact one article from a respected research marine biologist said intensity is more important than spectrum!

 

[kurt_n]

Google articles by 'Dana Riddle'. I think you'll find a lot of info on this specific topic.

 

[Perth_reefer]

kenpaw, I'll ask you to accept my humble apology. I did some more research and it appears that intensity does make a difference. I stand corrected. In fact one article from a respected research marine biologist said intensity is more important than spectrum!

Yeah that's fine mate. The article I read, it was a while ago now but it stated something about that we should be looking at DLI which is Daily Light Integral, a combination of intensity and photoperiod.