Split lighting schedule for more growth?

[avaneaton2000]

Here is something for the RC brain trust, I read an article a while back and now I can't find it about using a split lighting schedule of two blocks of roughly six hours of lighting with four to six hours of darkness in between to increase growth in corals. That assumption is based on the statement that corals reach a point of saturation in their photosynthesis around four to six hours of lighting (again from the article that I can't find).

What do you guys think about this?

(There are no fish in the tank to throw off their cicadian rhythm)

I know some people do this if their tanks are running hot but has anyone seen increased growth?

The best way to test this would to have two identical frags on the same system one with regular 8-12 hour light and one with two periods of 4-6 hours. That way the variables would be kept to a minimum

I look forward to your responses and experiences

 

[zdawgnight]

I personally have not done the research but I had read a posting by someone who had tried this from the sps forum. From what I understood It appeared that there was no extra growth from changing the photo period around. I am not a scientist or biologist but it makes sence to me that the corals have been living in the oceans for thousands of years and to my knowledge there has never been a time where the sun was up for 6 hours, and twice in one day. Hopefully my post doesnt sound pushy or mean. But it makes seems to me that an animal that has evolved to its surroundings over such a long time, would thrive in the same enviroment not a double day situation.
That is my personal belief obviously I have no phds to back me up just trying to contribute. If someone were to test this hypothesis I would be very interested to hear the outcome as well.

 

[MCsaxmaster]

Unfortunately this idea gets passed around alot, but it is based on some fundamental misunderstandings about photosynthesis.

The principal misconception here is that photoperiod is an important factor an attaining saturating rates of photosynthesis. This arises from extrapolating real-world data without understanding the physiological mechanisms underlying the process.

Light is absorbed first by the pigment complexes around photosystem II. The energy is transferred to the reaction center, H20 is split to O2 and H+ and electrons are transferred to photosystem I with plastoquinone. At PSI the electrons and H+ are used to reduce NADP+ to NADPH which is further used for a variety of cellular processes, such as fixing CO2.

There are two important rate-limiting steps here: 1) the capture of light energy, and 2) the transfer of electrons from PSII to PSI. The first step depends on light intensity while the second depends on the size of the plastoquinone pool.

The absoprtion of light takes on the order of 10^-12 seconds. For our purposes, that is instantaneous. The transfer of electrons from PSII to PSI is slower, but still on the order of fractions of a second, typically.

In other words, beyond fractions of a second, photoperiod is simply not an important factor in determining the rate of photosynthesis. The driving factors are: 1) the light intensity, and 2) the plastoquinone pool. This is true of instantaneous rates of photosynthesis. Over longer time scales organisms do adapt to ambient conditions and thus change their intrinsic rates of photosynthesis under given conditions, but that is beyond the present consideration. Besides, this adaptation is based almost entirely on ambient light intensity.

So if photoperiod, beyond a few seconds, is not an important driver in the rate of photosynthesis, where does the idea come from?

Corals in nature do indeed tend to experience increasing rates of photosynthesis after sunrise (as does everything) finally reaching saturated rates of photosynthesis typically after several hours. The important factor here is not the photoperiod, but rather the changing intensity. When the sun rises the light intensity is initially dim. As the sun climbs higher in the sky the intensity rises and the rate of photosynthesis rises until, eventually, the light intensity is high enough that it is saturating to photosynthesis. Photoperiod simpy has nothing to do with it and light intensity has everything to do with it.

For example, if you were to cover a coral in a dark box all morning and uncover the coral at noon it would take on the order of seconds, at most, to reach a saturated rate of photosynthesis, not hours. The light intensity is plenty to saturate photosynthesis. It doesn't matter if the coral has been exposed to light for many hours or a few seconds: if the light is bright enough, it is bright enough.

When we turn on the lights over our corals, assuming our light sources produce light bright enough to saturate photosynthesis (metal halides and T5's are definitely bright enough under most circumstances) the corals become saturated with light essentially instantaneously and the rate of photosynthesis remains at a similar rate for as long as the light is on (assuming some other factor does not become limiting).

Thus, 6 hrs on, 6 hrs off, 6 hrs on, 6 hrs off, won't lead to any significant difference in net primary production as compared to 12 on, 12 off or whatever combination you like, as long as there are 12 hrs of light. There simply isn't a good reason to think that the two should be qualitatively any different in their effects.

The only way in which I can conceive that a person might see a difference is if the corals are experiencing photoinhibition. If the light source is too bright it can cause damage to the corals due to the build-up of reactive oxygen species and molecular O2 in the tissues. In that case splitting up the photoperiod might allow the coral to dissipate some of these nasty species and recover after a light period. Thus, 6:6:6:6 onffnff could end up having different effects than 12:12 onff. We might see something similar with insufficient water flow, or food, or etc.

I would suggest here that the way to fix the problems is not to blast the corals with too much light or given them too little water flow, food, etc.

For practical purposes, no, this will not work. The very premises the idea is based on are flawed.

 

[avaneaton2000]

I understand your dissertation on why you say this won't work, but do you have any first hand experience with this?

There are a lot of people who are propagators and coral farmers that swear by spit light schedules for more growth. Also the Article that I read about this was posted here on RC. A. Calfo has also written articles about the benefits of split lighting so...

Any one else have EXPERIENCE positive or negative with split lighting?

Thanks,

Adam

 

[MCsaxmaster]

<a href=showthread.php?s=&postid=12113270#post12113270 target=_blank>Originally posted</a> by avaneaton2000 I understand your dissertation on why you say this won't work, but do you have any first hand experience with this?

No...why would I try something if I already know it is almost certainly not going to benefit my corals, and puts excessive ware on the bulbs?

Do I have to try praying to Ra before I can conclude that doesn't work either?

There are a lot of people who are propagators and coral farmers that swear by spit light schedules for more growth.

There are also folks that are coral farmers and propagators that swear by aragamight, coral vital, and anything else one can think of. That doesn't mean any of those products/methods are doing something beneficial beyond what is conceived in the aquarists mind

Also the Article that I read about this was posted here on RC. A. Calfo has also written articles about the benefits of split lighting so...

Everyone is occasionally mistaken about something. If Anthony is making those claims the onus is on him to provide evidence, because the physiology flat out contradicts the idea

Any one else have EXPERIENCE positive or negative with split lighting?

Thanks,

Adam

Consider: what if folks were suggesting that dipping corals very briefly in boiling water was a good way to rid them of parasites. Do I have to have experience dipping corals in boiling water and watching them instantly die in order to know it's a bad idea?

The physiology here is pretty clear. An understanding of physiology is what brings us modern medicine. Personal experience got us witch doctors :lol:

 

[avaneaton2000]

What wear on bulbs? 6+6=12 or 12=12 don't need to be a rocket scientist for that.

Even if you can sight you hard "facts", I am still willing to experiment, because experimentation is what got us modern medicine.

Please don't post again, this thread is not to get into a ****ing match with you but to hear from people that have FIRST HAND EXPERIENCE with this.

Thanks,

Adam

"If you can't go to college go to State" you know what I am talking about

 

[shelburn61]

<a href=showthread.php?s=&postid=12118998#post12118998 target=_blank>Originally posted</a> by avaneaton2000
What wear on bulbs? 6+6=12 or 12=12 don't need to be a rocket scientist for that.

Even if you can sight you hard "facts", I am still willing to experiment, because experimentation is what got us modern medicine.

Please don't post again, this thread is not to get into a ****ing match with you but to hear from people that have FIRST HAND EXPERIENCE with this.

Thanks,

Adam

"If you can't go to college go to State" you know what I am talking about

#1
Most of the wear on bulbs occurs during startup so 6+6 does not equal 12 in this case.

#2 MCsaxmaster knows what he is talking about and has more business posting in an advanced forum than you No matter what you may have read, this question is still bound by basic coral biology and photosynthesis... which he tried to explain to you.

One thing he did not address, is that the intermitent dark period might provide a recuperative period during which the corals might be replenishing levels of other compounds. Photosynthesis is not necessarily equal to growth and perhaps this "rest period" allows the coral use products of photosynthesis more efficiently...

 

[mesocosm]

Greetings All !


Chris ... they made you read Plato's The Cave as an undergrad, yes? If you'll recall, the folks who spent their lives chained in darkness watching shadows didn't offer endless virgins and piles of gold to the one who set them free ... they tore him limb from limb in a frenzy of anger and fear. The ancient Greeks were pretty astute observers of Human behavior.

How about a nice bowl of fruit loops? You'll feel better ... :lol: :rollface: ...

<a href=showthread.php?s=&postid=12119371#post12119371 target=_blank>Originally posted</a> by shelburn61
... MCsaxmaster knows what he is talking about ...

Indeed ... :thumbsup:

For those who aren't familiar with his background, Chris Jury (MCsaxmaster) is one of the brightest & refreshing reason-based voices to emerge in English-speaking reefkeeping cyber communities in the last decade. He has studied under some of the most advanced marine biology researchers in the world, has had field research experiences that some of us might kill to have, and has published a series of articles on bacteria and biogeochemical cycling in RC's Reefkeeping Magazine ... his perspective is not to be dismissed lightly. Indeed, his posts are of significant value to anyone wishing to emerge out of the darkness of anecdotal myth-information into the wonderous twilight where science theory blends with practioneer mastery.

Happily, this hobby-addiction of ours remains more art than science ... divergence of perspective within any artistic community is to be expected. Don't be afraid. This is a good thing. Even so, the science is the science ... ignore the empirical data at the peril of your animals' productivity, and of your bank account's balance.

JMO ...

<a href=showthread.php?s=&postid=12118998#post12118998 target=_blank>Originally posted</a> by avaneaton2000
What wear on bulbs? 6+6=12 or 12=12 don't need to be a rocket scientist for that. ...

Do a little reading on what happens to the chemical lining inside bulbs when they're first fired up. Project what happens with bulbs fired at 2X the rate of another bulb. What you discover may be of use to you as you make bulb selections, and chart out bulb replacement timelines.

<a href=showthread.php?s=&postid=12118998#post12118998 target=_blank>Originally posted</a> by avaneaton2000
... Even if you can sight you hard "facts", I am still willing to experiment, ...

Wow ... experimentation that purposefully ignores relevant empirical data and historical analysis. Good luck with that. May the force be with you.

<a href=showthread.php?s=&postid=12118998#post12118998 target=_blank>Originally posted</a> by avaneaton2000
... to hear from people that have FIRST HAND EXPERIENCE with this. ...

I'm a biologist currently cultivating WC Bali, WC Indonesia, and captive cloned broodstock strains of Entacmaea quadricolor for a medium-scale aquaculture operation. One of the many variables that I'm looking at is the kind alternating photoperiod sequences that you're interested in ... but not with the intent of maximizing phtosynthesis rates. Photosynthesis (max) is a function of intensity as Chris has already pointed out. My other interests (potentially related to photoperiod manipulation) have to do with the acclimation of WC BTA specimens, minimizing exploratory movement, manipulation of expansion-contraction patterns, pigmentation synthesis, increasing growth rate, and maximizing stored energy reserves.

As shelburn61 has already pointed out, photosynthesis (max) does not imply growth (max). Were there other aspects of this topic that you're interested in?



JMO .. HTH
:thumbsup:

 

[MCsaxmaster]

Oh well; you can lead a horse to water...

One thing he did not address, is that the intermitent dark period might provide a recuperative period during which the corals might be replenishing levels of other compounds.

Indeed, this is an interesting point that I alluded to, but didn't say much about. Really though, in order for there to be a benefit to a "recuperative" period the corals need to be experiencing photoinhibition. If the light intensity is very strong then by braking up the light period it might make it easier for the coral to manage the build-up of reactive oxygen species and molecular O2. At least maybe, and that in is a reasonably sized maybe. However, at anything but very high light intensity (or UV) that point becomes moot

As for being able to replenish compounds in the dark that were used in the light: which ones? Why aren't these replenished at a sufficient rate in light? Why does the dark allow replenishment? I'm skeptical this could play a role

Photosynthesis is not necessarily equal to growth and perhaps this "rest period" allows the coral use products of photosynthesis more efficiently...

How? Why? It seems to me that trying to invoke such explanations without obvious hard evidence that would lead us to invoke them lends toward trying to shoe-horn evidence behind an idea that simply isn't supported by the evidence.

Best,

Chris

p.s. Thanks for the kind words guys!

 

[Big E]

The bulbs in our aquarium are stationary & not like the sun which is constanly changing it's postion in referance to the coral..........so the intensity level is instantaneous after the bulb is running for 15 minutes or so & the postion never changes. Photo inhibition would seem likely over too many hours of exposure.

So it's possible that there isn't much more growth in a aquarium that lights a coral for 6 hours vs. 12. At the very least I would think if this were put on a scale it would show diminishing returns as the last six hours clicked by.

If the coral is getting all the light it needs for optimal growth at the 6 hour point & also gets the right amount of dark hours it needs, it's possible you could create essentially two days of growth in a 24 hour period with the two six hour blocks.

The optimal number of hours of light & darkness for the coral is what would be important. It's possible the number is lower than 6 hours. There's also a number of other factors to consider like water clarity & the the positioning of the coral in reference to the distance it sits from the light.

The question that needs to be anwsered is how many hours can a coral endure before the light is damaging it & not helping it grow?
If the coral is damaged beyond 6 hours this could be why propagators say they are getting better growth with the split system.........they are no longer damaging the coral by knocking off 6 hours of continuous light. The coral's energy is being used for growth instead of being used for repair/recuperation.

 

[avaneaton2000]

Thank you Big E, that is exactly what I am talking about! I am with you and I am going to try some experiments and track the results, which would be the only way to see if there is a difference.

 

[MCsaxmaster]

Goodness gracious,

The bulbs in our aquarium are stationary & not like the sun which is constanly changing it's postion in referance to the coral..........so the intensity level is instantaneous after the bulb is running for 15 minutes or so & the postion never changes.

Ok, but is this necessarily a bad thing? Trying to even out the light field a bit is probably not a bad idea insofar as that will generally lead to more natural looking coloration and growth form, which I think most folks would regard as pleasing. Strictly speaking though, why would a fixed lighting angle and intensity be in any way detrimental?

Photo inhibition would seem likely over too many hours of exposure.

How? Why?

So it's possible that there isn't much more growth in a aquarium that lights a coral for 6 hours vs. 12. At the very least I would think if this were put on a scale it would show diminishing returns as the last six hours clicked by.

Why?

Moya et al., 2006 used nubbins of Stylophora pistillata to look for a diel cycle in coral calcification. Whether the corals were exposed to 4, 8, 12, 16, or 20 hrs of light the rate of calcification was constant during the light period and about 3x the rate of dark calcification, which was also constant. Thus, the highest net daily calcification was obtained after a 20 hr light period and the lowest net daily calcification was obtained after a 4 hr light period.

There was nothing like deminishing returns observed: the longer the light period the longer the period of light enhanced calcification and the higher the daily net calcification. The correspondence was 1:1.

If the coral is getting all the light it needs for optimal growth at the 6 hour point & also gets the right amount of dark hours it needs, it's possible you could create essentially two days of growth in a 24 hour period with the two six hour blocks.

But there's no evidence whatsoever that net daily growth, calcification or photosynthesis plateau after 6 hrs, nor do I see any reason that is even hypothetically likely. In fact, we have direct evidence that IS NOT the case (see above).

The optimal number of hours of light & darkness for the coral is what would be important. It's possible the number is lower than 6 hours. There's also a number of other factors to consider like water clarity & the the positioning of the coral in reference to the distance it sits from the light.

How would you determine the optimal number of hours of light? How would you define optimal? What evidence is there that it is possible to obtain similar net calcification in a photoperiod of 6 hrs or less as compared to 12 hrs or more? Moya et al., shows experimental evidence that flat-out contradicts that premise.

The question that needs to be anwsered is how many hours can a coral endure before the light is damaging it & not helping it grow?

Except at very, very high light intensities (relative to what the coral is adapted to) why would photoperiod matter at all? At or below saturating light intensity, photosynthesis doesn't provide a net stress.

If the coral is damaged beyond 6 hours this could be why propagators say they are getting better growth with the split system.........they are no longer damaging the coral by knocking off 6 hours of continuous light. The coral's energy is being used for growth instead of being used for repair/recuperation.

But where's the evidence that is even logically tenable? Corals in nature that are exposed to much, much higher light intensity than we provide in captivity may experience significant photoinhibition for as much as 6 hrs per day, yet they still maintain among the highest rates of calcification of any corals on the reef.

I mean, if you know of any experimental evidence that suggests that a split light cycle or a shortened light cycle do in fact yield similar or higher rates of calcification, by all means cite it. But lacking that, I think we really have to go with the experimental evidence that is available, all of which flat-out contradicts the ideas that a split light cycle is beneficial or that a short photoperiod is equavalent or better than a normal photoperiod.

Chris

 

[MCsaxmaster]

<a href=showthread.php?s=&postid=12127688#post12127688 target=_blank>Originally posted</a> by avaneaton2000
Thank you Big E, that is exactly what I am talking about! I am with you and I am going to try some experiments and track the results, which would be the only way to see if there is a difference.

By all means, go for it. This wouldn't be a difficult study to do, given some space and time. Obviously you'll need to quantify calcification. A great way to do this is using the buoyant weight technique, but that isn't particularly practical for at-home use. Just measuring linear extension of braches with a ruler/calipers could be used.

If you plan to run a little experiment I'd seek a great deal of input first, and from working scientists (biologists, ideally). Without a sound experimental design, the efforts will be for naught.

Chris

 

[avaneaton2000]

To perform this experiment I would have multiple frags from a single mother colony in the same tank with a black acrylic divider between the groups. One side gets 12/12, one side gets 6/6/6/6, Identical bulbs and fixtures above.

What else should I do to remove as many variables as possible?
What schedule should I light the fuge? 24/7 would seem to be the only way that would be fixed and not a variable.

Help me prove my theory wrong don't just shoot it down.

Thanks

By the way I was joking about the state comment, I have a lot of friends who went there and I went there for their hockey camps.

 

[MarkPo]

FWIW, over in planted freshwater tanks, the split photoperiod is fairly common(Well, most people have heard of it, not sure how many people actually use it). I've run several tanks this way, including 2 of my current ones. However, I don't think anyone ever suggested it's better for the plants.

Instead, it's used to have the lights on for viewing both before work and into the evening, without a 16 hour photoperiod. Purely for the benefit of the aquarist, not the plants.

I do not run my reef this way.

 

[xJake]

I believe the split photo-period run on planted tanks is to prevent algae growth. The idea behind it is that the algae cannot adapt to the split lighting schedule whereas the plants can therefore reducing algae growth. Obviously I have no scientific evidence to back this up but I have run my planted tank like this for years - algae free. (After being plagued by hair algae for the first few months)

As for the split lighting schedule on a reef tank I see no benefit based on what others have posted. One benefit that may be possible is the same goal of a planted tank's split schedule and that is to curb nuisance algae growth, however, I have no idea of the science behind what causes the algae growth to be curbed in planted tanks and therefore have no knowledge of the same in reef tanks.

 

[yangsha]

wow

 

[airinhere]

I think an old thread I had posted to was the RC thread the OP was talking about.

I had started using a dual light cycle and experienced great growth rates (especially with zoanthids). MCsaxmaster was kind enough to give me some useful insight into what it was I had observed, and the consensus at the time was that it probably wasnt really any more or less effective than a regular light cycle.

I do still run the dual light cycle. I get good growth from my corals. But I take pretty good care of my tanks also. Is my growth related to my light cycle? Maybe. Maybe not.

But I like that I get up in the morning to a lit tank, come home from work to a lit tank and when the lights go out around midnight, I am headed to bed.

I think any effort to find a magic bullet that makes corals grow like wild, or that causes algae to wither and die is probably hopeful thinking.

Take a dual light cycle for what it is. A convenient way to view your tank without running the lights for 18 hours a day.

 

[MCsaxmaster]

<a href=showthread.php?s=&postid=12131558#post12131558 target=_blank>Originally posted</a> by avaneaton2000
To perform this experiment I would have multiple frags from a single mother colony in the same tank with a black acrylic divider between the groups. One side gets 12/12, one side gets 6/6/6/6, Identical bulbs and fixtures above.

What else should I do to remove as many variables as possible?
What schedule should I light the fuge? 24/7 would seem to be the only way that would be fixed and not a variable.

Help me prove my theory wrong don't just shoot it down.

Thanks

By the way I was joking about the state comment, I have a lot of friends who went there and I went there for their hockey camps.

This is potentially an easy study to perform as long as a few considerations are made. As you suggest, I'd setup the system by either dividing a single tank with an opaque divider, or in adjacent tanks on the same system with an opaque divider between them. An easy way to do this would be to feed a couple of 10 gal tanks off a larger system.

You'll need to ensure that all the nubbins are receiving similar light intensity regardless of treatment. The better the photometer the better the measurment, but the important thing is that light intensity is the same (to within a small margin of error) for all nubbins over the course of the experiment. Since turning bulbs on is what constitues much of the ware on the bulb, the bulbs that are being turned on twice a day instead of once a day will most likely ware out faster and hence will experience a faster decline in intensity. This needs to be measured and compensated, otherwise the results will be useless.

Any easy way to help ensure that the bulbs aren't waring out faster or slower on either side would be to switch the bulbs for the two treatments every few days. You'll still need to be measuring light intensity, but this should make things easier and help remove an artifact of manipulation.

Probably the biggest hurdle to overcome is how growth is measured. There are many good techniques, but most require laboratory equipment that may not be readily available to most folks. For example, measuring calcification as the change in buoyant weight of the nubbins is an easy and pretty effective, but requires a sensitive balance that is properly equipped.

Perhaps the best way to get around that would be to use just very small nubbins that constitute just the very tips of branches from a branching coral. For instance, if you had a single colony of Seriatopora hystrix you could take the last 1 cm of strait branches (as opposed to branches that are beginning to bifurcate) and make a bunch of nubbins.

Another option might be to use a dremel or band-saw to make equally sized squares of a plating Montipora sp. (say 1x1 cm squares). From a modestly sized colony you could make many little nubbins. I'd either use pieces that are all derived from the growing edge of a colony or from the interior though, not both. You don't want to be comparing a bunch of young, growing tissue to some other older, senescent tissue.

Either way, you could track growth by photographing each nubbin every week as well as measuring linear extension with calipers or a ruler.

I'd use a bare minimum of 5 nubbins per treatment.

Track growth for a month or two and see what you get. I'd then repeat everything by switching the tanks (the tank or side of tank that was 12:12 becomes 6:6:6:6 and vice versa) and see if you get the same result. If you do, then altered photoperiod is most likely causing the pattern you see. If not, it's sort of back to square one and figuring out why the results arent' replicable.

Chris

p.s. I guess I missed the crack on state schools above. Ha, I went to MSU because it was my top choice. It was my top choice because it has better programs for my areas of interest as compared to the other schools I was considering, such as U of M. There may have been a time when state schools were not as good as other institutions, but that time has long ago passed...

 

[shelburn61]

MCsax,

As I recall, the light intensity necessary to reach saturation or even photoinhibition is pretty attainable with aquarium metal halides. Correct? (I can't find the article I am thinking of...)