Photo-Period Question

[Ryan S]

If you run lights 6 hours per day vs 12 hours per day (100% intensity), would you see faster growth with the longer photo-period? Is there such a thing as too long of a photo-period? What if you ran lighting for 18 hours a day with 6 hours off, for example?

[jaddc]

There was a paper published in June on this wrt to Galaxea. I'll copy the abstract (summary) below. Essentially, the photoperiod or intensity did not affect growth rate in their work. Having the lights on for 24 hours killed the coral. I'm working on getting the paper.

 

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Light intensity, photoperiod duration, daily light flux and coral growth of Galaxea fascicularis in an aquarium setting: a matter of photons?Author(s): Schutter, M (Schutter, Miriam)^1,2; van der Ven, RM (van der Ven, Rosa M.)¹; Janse, M (Janse, Max)³; Verreth, JAJ (Verreth, Johan A. J.)¹; Wijffels, RH(Wijffels, Rene H.)²; Osinga, R (Osinga, Ronald)¹Source: JOURNAL OF THE MARINE BIOLOGICAL ASSOCIATION OF THE UNITED KINGDOM Volume: 92 Issue: 4 Special Issue: SI Pages: 703-712 DOI:10.1017/S0025315411000920 Published: JUN 2012

 

Abstract: Light is one of the most important abiotic factors influencing the (skeletal) growth of scleractinian corals. Light stimulates coral growth by the process of light-enhanced calcification, which is mediated by zooxanthellar photosynthesis. However, the quantity of light that is available for daily coral growth is not only determined by light intensity (i.e. irradiance), but also by photoperiod (i.e. the light duration time). Understanding and optimizing conditions for coral growth is essential for sustainable coral aquaculture. Therefore, in this study, the question was explored whether more light (i.e. more photons), presented either as irradiance or as light duration, would result in more growth. A series of nine genetically identical coral colonies of Galaxea fascicularis L. were cultured for a period of 18 weeks at different light duration times (8 hours 150 mu E m(-2) s(-1):16 hours dark, 12 hours 150 mu E m(-2) s(-1):12 hours dark, 16 hours 150 mu E m(-2) s(-1):8 hours dark, 24 hours 150 mu E m(-2) s(-1):0 hours dark) and different irradiance levels (8 hours 150 mu E m(-2) s(-1):16 hours dark, 8 hours 225 mu E m(-2) s(-1):16 hours dark and 8 hours 300 mu E m(-2) s(-1): 16 hours dark). Growth was determined every two weeks by measuring buoyant weight. Temperature, salinity and feeding levels were kept constant during the experiment. To detect possible acclimation of the corals to an increased light duration, rates of net photosynthesis and dark respiration were measured, hereby comparing coral colonies grown under an 8:16 hours light (150 mu E m(-2) s(-1)): dark cycle with corals grown under a 16:8 hours light (150 mu E m(-2) s(-1)): dark cycle. No increase in growth was detected with either increasing photoperiod or irradiance. Continuous lighting (24 hours 150 mu E m(-2) s(-1):0 hours dark) resulted in immediate bleaching and the corals died after 14 weeks. Hourly photosynthetic rates were significantly reduced in the 16 hour light treatment compared to the 8 hour light treatment. As a result, daily net photosynthetic rates were not significantly different, which may explain the observed specific growth rates. Acclimation to photoperiod duration appeared neither to be mediated by changes in chlorophyll-a concentration nor zooxanthellae density. Based on the results of this study, we can conclude that the enhancing effect of light on coral growth is not only a matter of photons. Obviously, the availability of light was not limiting growth in these experiments and was probably in excess (i.e. stressful amounts). Other factors are discussed that play a role in determining growth rates and might explain our results.

[Jon Lazar]

Academic papers like this should be pinned in the Education section. There's way too much anecdote, opinion, urban legend, and sales pitch in this hobby; especially when topics like this are addressed by peer-reviewed scientific papers.

 

I can think of a few other papers off the top of my head: the lifecycle of acropora eating flatworms, the effect of crabs in acropora corals, the connection between carbon fines and HLLE, and now this one. I'm sure there's many more that apply to the average hobbyiest and aren't too technical.

 

How do we as a club get better access to real studies with controls and peer-reviewed papers, and make them accessible to our members?

[Origami]

Ryan, this may be of interest:

http://www.wamas.org/forums/topic/30579-amazing-coral-growth-due-to-new-lighting-schedule

[Ryan S]

Interesting stuff. I was getting ready to increase my photo-period from 12 hours to 14 hours! I will reduce it from 12 to 8 instead, and see how the tank responds!

 

[Ryan S]

I found another 2 articles on point:

 

http://www.fishchannel.com/saltwater-aquariums/aquarium-frontiers/natural-reef-light.aspx

 

and

 

http://www.advancedaquarist.com/2009/5/aafeature

[jimlin]

cool, i am switching from 9 hrs to 8 hrs to see if there is a difference.

[Ryan S]

This post is also related to:

 

http://www.wamas.org/forums/topic/51407-poll-moon-light-on-light-fixture/

 

As many posters discuss here, which Tom posted, some suggest "the better growth comes from the prolonged night period".

 

I am all about trying new things. I am going to turn off my moon light entirely, and drop my photo-period from 12 hours to 8 hours. Will see how the tank looks in 1 month (if any change is noticeable by then).

Edited July 31, 2012 by Ryan S

[ToddR]

My lights are on from 3pm to 11pm. Any longer and I see negative results.

[Ryan S]

I'll try this for a month and see what happens. 8 hours total with 6 hours at 100% intensity 12k.

 

Edited July 31, 2012 by Ryan S

[BowieReefer84]

This post is also related to:

 

http://www.wamas.org...-light-fixture/

 

As many posters discuss here, which Tom posted, some suggest "the better growth comes from the prolonged night period".

 

I am all about trying new things. I am going to turn off my moon light entirely, and drop my photo-period from 12 hours to 8 hours. Will see how the tank looks in 1 month (if any change is noticeable by then).

 

You were running your led's at 100% for 12 hours? dang. I ran mine at like 5 1/2 hours not even full power.

[Coral Hind]

My light schedule for three 250w MH staggered for 8 hours each. I used to do the MH lights for 10 or 12 hours until we had a discussion here on the forums about eight years ago and most of us reduced the photo period.

 

MH1 - on 1200hrs

MH2 - on 1230

MH3 - on 1300

LED - on 1930 (blue 4x19w panarama pros)

MH1 - off 2000

MH2 - off 2030

MH3 - off 2100

LED2 - on 2159 (1w white)

LED - off 2200

LED2 - off 0600

 

I do think the light intensity needs to be factored in. When I was doing T5s and later tried LEDs I had to leave them on much longer to get the same effect as the MH lights.

[jaddc]

I got my hands on the paper I cited above. Here is the meat of the matter:

 

"No positive correlation between light availabilityand growth was observed under the given experimental

 

conditions. Neither with increasing photoperiod duration, nor

 

with increasing irradiance, nor with increased daily light flux.

 

This indicates that light was not the limiting factor for coral

 

growth and was most probably in excess."

 

 

 

 

So basically, if your tank has metal halides or LEDs, then your coral have enough light to grow. They point to other factors that may inhibit growth:

 

 

 

 

"Obviously, the availability of photons alone cannot

 

enhance coral growth. Besides the amount of photons, also

 

other factors may play a role in determining coral growth

 

rate. Factors known to be limiting for the growth of stony

 

corals include water flow (Lesser et al., 1994, Schutter et al.,

 

2011), aragonite saturation state (Gattuso et al., 1998;

 

Leclercq et al., 2000; Schneider & Erez, 2006) and its associated

 

components (Marubini et al., 2008), the availability of

 

essential trace metals such as copper and zinc (Ferrier-Page`set al., 2005) and/or the availability of essential nutrients such

 

as aspartic acid (Allemand et al., 1998) that are mostly supplied

 

by heterotrophic feeding (Houlbreque & Ferrier-Page`s,

 

2009). While factors known to have an inhibiting effect on

 

coral growth include elevated nutrient concentrations

 

(Ferrier-Page`s et al., 2000; Fabricius, 2005), increased iron

 

concentration (Ferrier-Page`s et al., 2001), increased temperatures

 

(Jokiel & Coles, 1990; Marshall & Clode, 2004), competition

 

(Rinkevich & Loya, 1985; Tanner, 1995) and

 

sedimentation (Rogers, 1990)."

 

 

 

 

Which is about what all the books tell us.

 

 

 

 

 

[GraffitiSpotCorals]

I just bumped mine up to 5 hours.

[Coral Hind]

Only 5 hours, what was it at before?

[jimlin]

why 5?

[GraffitiSpotCorals]

It was at 4.5 which I started when I had that crazy unknown cyano or whatever. I used to do I think 8 or 7 hours and haven't noticed a difference. I don't use a chiller so keeping the hours down helps with temperature (especially since my ac unit is junk and I am scared it's about to go). The main level gets hot enough running them for 5 hours and during the summer I think that's all the fans can keep up with.

[Chad]

Very interesting stuff!

 

Thanks for the info, Jeff!

[Coral Hind]

It is interesting but I would have liked to have seen some test with lower photo periods then their 8, 12, 16, and 24hrs. The difference between 4, 6, 8, and 10hrs would probably help us out more.

[jaddc]

You sound like a scientific peer reviewer!

 

Their focus was on aquaculture. So I assume that given limited resources they choose a time range that is most appropriate to growing coral.

[rocko918]

I only run my MH's for 6 hours. I found that i get the same results as when i ran them at 8 hours. cuts down on cost and heat.

[Coral Hind]

You sound like a scientific peer reviewer!

 

Their focus was on aquaculture. So I assume that given limited resources they choose a time range that is most appropriate to growing coral.

 

If their focus was on growing corals, which is what we aim to do here, then there is an issue because they tested for 12-24hr periods yet we seem to be running our tanks around 6-10hrs. So that kind of shows we are not lighting our tanks enough.

[jaddc]

Oh, I see what you are getting at.

 

From my understanding of their paper, the coral will aclimate to the light that is available in the tanks (to a point, assuming proper lighting fixtures for corals). The coral grown in 16 hours had the same growth at the 8 hours of light. To figure out why that was, they measured the hourly rate of photosynthesis and observed that the coral in the longer light period had a lower hourly rate of photosynthesis. So at the end of the day, the 8 hour and the 16 hour coral produce the same total amount of energy, and so total calcification rates were nearly equal.

 

So for equal power of lighting, the amount of time that the light is on really does not matter. I'm sure there is a minimum needed for survival, but if people can have their lights on for 6 hours and still have growth, I'd surmise that 6 hours is sufficient, right? So then in the 6 hour period the coral ramp up their hourly rate photosynthesis to compensate for the short day.

 

Because the values of photosynthesis did not change dramatically over the 8, 12, 16, and 24 hour time periods, my guess is that the difference in growth between 6 hours and 8 hours and even 16 hours would not be noticeable.

 

My take home is that as long as we use the correct lighting (LEDs, metal halides...), the coral will grow. We need not be concerned about how long the lights are on. I think that is pretty cool, because now we can make that lighting decision based on other factors -- heat transfer, our wallets, when it's convenient for us to view the tank...etc.

[Ryan S]

It's only been 3 weeks, but since I reduced my photo period from 10 to 6 hours, I've really seen obvious improvement in my SPS corals. Their colors and growth are very apparent. What were 1" frags with no encrusting for 2 months, have now almost fully encrusted the frag plugs, and the brown pieces actually have colors now. I'll continue to monitor them, but so far the results have been very good.

[onux20]

It's only been 3 weeks, but since I reduced my photo period from 10 to 6 hours, I've really seen obvious improvement in my SPS corals. Their colors and growth are very apparent. What were 1" frags with no encrusting for 2 months, have now almost fully encrusted the frag plugs, and the brown pieces actually have colors now. I'll continue to monitor them, but so far the results have been very good.

Do you have before and after pics?