PAR intensity vs time lights are on

scoopsthedog

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From what I've read the PAR (and temp) setting is the most important thing as far as lighting and corals go. Is there an optimum time to keep the lights on where any longer doesn't help and only promotes algae bloom and any less doesn't allow coral to get the full amount of light?

Also what's the difference between "Moonlight" which they say you can leave on for four hours and regular Blues for running during the day (assuming intensity levels)?
 

Rory's Reef

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Aquarium Lighting: Moonlight - A Concise Review of Its Spectrum, Intensity, Photoperiod, and Relationship to Coral and Fish Spawning

This is a good article. If you're not interested in reading the whole article, you could probably just get away with reading the conclusion.

As far as length, that's something I'm interested in as well. I've read in other forums that some people believe 12 hours is the max you would want to have your lights on with most people falling around 10 - 11 hours. But I'm interesting in learning more.
 

mcarroll

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If you're doing a sunrise/sunset, then 12 hours would do it.

Something like this:
PSHCurve.gif

From: http://www.solar-designs.com.au/thedetails.shtml

What that shows is that if you have a plain light that turns on and off (no sunrise/sunset effect) but provides the same intensity as the sun (2000 PAR = 1000 W/m2 = 100,000 lux), then it only needs to run for around five hours per day to provide the same amount of light as a 12 hour day "with dimming".

If your light only provides about half of that intensity (typical of commercial lights at "100%"), then a ten hour day would be suggested.

Make sense?

(You still need a light meter to set it correctly.) :)
 

bif24701

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If you're doing a sunrise/sunset, then 12 hours would do it.

Something like this:
PSHCurve.gif

From: http://www.solar-designs.com.au/thedetails.shtml

What that shows is that if you have a plain light that turns on and off (no sunrise/sunset effect) but provides the same intensity as the sun (2000 PAR = 1000 W/m2 = 100,000 lux), then it only needs to run for around five hours per day to provide the same amount of light as a 12 hour day "with dimming".

If your light only provides about half of that intensity (typical of commercial lights at "100%"), then a ten hour day would be suggested.

Make sense?

(You still need a light meter to set it correctly.) :)

10 hours per day at peak intensity?
 

mcarroll

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Depending on what your peak intensity is, yes maybe. :)

(Generally we don't shoot for 2000 PAR as our goal, so there's that to consider as well.)
 
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scoopsthedog

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Watch this video but Dana Riddle. It speaks to that.


This is a great video- a must watch for all reefers. My only thought is having just left Kauai the water movement, temp and tide pool zones are nothing like reefs in FL and places like Caribbean. I'm sure much of this applies to many coral but in places where there is additional light probably lower flow helps. Also what a great forum, tons of great replies and thanks to everyone for their POV. Sounds like intensity is def. the most important and afterwhile keeping lights on longer is really just for us as most coral reach peak intensity (PAR) at a few hours between dusk and dawn (12 hour day may only have 4 hours at peak). I may now invest in a more sophisticated controller to try and mimic nature.
 
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scoopsthedog

scoopsthedog

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If you're doing a sunrise/sunset, then 12 hours would do it.

Something like this:
PSHCurve.gif

From: http://www.solar-designs.com.au/thedetails.shtml

What that shows is that if you have a plain light that turns on and off (no sunrise/sunset effect) but provides the same intensity as the sun (2000 PAR = 1000 W/m2 = 100,000 lux), then it only needs to run for around five hours per day to provide the same amount of light as a 12 hour day "with dimming".

If your light only provides about half of that intensity (typical of commercial lights at "100%"), then a ten hour day would be suggested.

Make sense?

(You still need a light meter to set it correctly.) :)
The one thing i've noticed is that many of the reefers and LFS running new LED's never run them at 100% as they tend to be overkill- the video above actually states that out of all the parameters flow and ALK may be more important than high PAR (his tests show after 300PAR photosynthesis peaks out). They showed a 40% increase in photosynthesis with increasing flow and ALK to 12 vs bumping lights up past 500 PAR (which actually hurt the coral). These were also coral that lived both in tidal zones (getting huge amounts of PAR all day) and in deeper reef zones (lesser PAR).
 
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scoopsthedog

scoopsthedog

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Aquarium Lighting: Moonlight - A Concise Review of Its Spectrum, Intensity, Photoperiod, and Relationship to Coral and Fish Spawning

This is a good article. If you're not interested in reading the whole article, you could probably just get away with reading the conclusion.

As far as length, that's something I'm interested in as well. I've read in other forums that some people believe 12 hours is the max you would want to have your lights on with most people falling around 10 - 11 hours. But I'm interesting in learning more.

From the video above looks like it's 300PAR maximizes photosynthesis for many coral. Figure in a 10-12 hour day light cycle maybe 2-3 hours on each end are at 0%-40% of peak (dawn and dusk). Seems like flow and ALK really impact it as well and if there is heavy light and you increase those things could be a problem (again this seems pretty general as different corals clearly have different needs. Not much SPS in Hawaii).
 

mcarroll

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Some of the papers I've read mention that corals are shutting down photosynthesis by 9am....already photosaturated.

I think I've seen about 30 minutes mentioned for sunrise/-set.

I haven't personally seen a study that specifically compared elevated alkalinity, but elevated temperature and nutrients can do it in at least some cases.
 

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From the video above looks like it's 300PAR maximizes photosynthesis for many coral. Figure in a 10-12 hour day light cycle maybe 2-3 hours on each end are at 0%-40% of peak (dawn and dusk). Seems like flow and ALK really impact it as well and if there is heavy light and you increase those things could be a problem (again this seems pretty general as different corals clearly have different needs. Not much SPS in Hawaii).
Increasing flow decreases damage done by having lights too high. I helps carry away excess waste from the hosted algae.
 

griff500

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I would have thought that the high PAR from the sun is offset by the flow and surface movement, which are on a different level to our tanks, so far lower PAR would get the same results.
 

BlueCursor

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In the wild, any coral growing under 30 feet deep is not affected by surface movement. Really, only the top 15 feet of growth is highly impacted by the surface. When we scuba dive, at 30+ feet we don't care what is going on at the surface because we never feel it. We only feel currents. Those rarely are over 3 knots. A human with scuba fins cannot really outswim a 3 knot current. So most everywhere we scuba dive and see great corals is medium to low flow. We only need higher flow in our tanks to offset light stress and for things like slimers, that are used to surface turbulence.
 

griff500

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I disagree that we only need higher flow to 'offset light stress'. Higher flow helps corals to take up nutrients, which is rather important. Surface turbulence is useful for oxygen and helps to enable higher light intensity.
 

TheEngineer

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In the wild, any coral growing under 30 feet deep is not affected by surface movement. Really, only the top 15 feet of growth is highly impacted by the surface. When we scuba dive, at 30+ feet we don't care what is going on at the surface because we never feel it. We only feel currents. Those rarely are over 3 knots. A human with scuba fins cannot really outswim a 3 knot current. So most everywhere we scuba dive and see great corals is medium to low flow. We only need higher flow in our tanks to offset light stress and for things like slimers, that are used to surface turbulence.
You've never gone diving in the Florida current then :) It gets ripping pretty good even at 100 feet.
 

BlueCursor

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There are exceptions, but when you consider the size of the Atlantic ocean and the limited size of the gulf current, generally speaking there is little current outside of the surf zone.

Bonaire, which has much better coral life than the FL and Cozumel put together, has no current to speak of. The south china sea has little to no current in popular dive sites, yet again has better coral life than FL and Cozumel with their gulf coast.

Don't get me wrong, water movement in important in our tanks, but it's a bigger necessity due to over lighting and low nutrient water.
 

BlueCursor

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What do you mean by light stress? And are you talking about surface agitation?
Here is a link that goes into more detail: http://www.advancedaquarist.com/2006/9/aafeature2

It you look at Figure 8 under the section "The more light a coral receives, the more flow it will need", you will see the minimum flow required as determined by the study. Table 1 shows amount of flow in relation to photo inhibition and light intensity. Photo inhibition is the result of photosynthesis byproducts in high amounts of light. But Table 1 shows that in higher flows, there is less inhibition.

This study suggests a minimum flow of 7.4cm/s for PAR 300 and 10 cm/s for a PAR of 400. 2.54 cm = 1 inch, so we are looking at 3+ in/s of flow.
 

griff500

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There are exceptions, but when you consider the size of the Atlantic ocean and the limited size of the gulf current, generally speaking there is little current outside of the surf zone.

Bonaire, which has much better coral life than the FL and Cozumel put together, has no current to speak of. The south china sea has little to no current in popular dive sites, yet again has better coral life than FL and Cozumel with their gulf coast.

Don't get me wrong, water movement in important in our tanks, but it's a bigger necessity due to over lighting and low nutrient water.

We are talking about the flow found where corals that we try to keep are prolific and that will surely tend to be in areas of higher flow.

I have to disagree with your last sentence. High flow isn't only required due to over-lighting and low nutrient water - it directly increases respiration, which increases photosynthesis and calcification and, as you have quoted, reduction of photoinhibition. We want our corals to thrive rather than merely survive and so high flow with high light are required for SPS with that goal in mind. You seem to be arguing against high flow being required for SPS in our tanks based on them being found growing in other conditions, but that isn't our goal and corals can survive in less than ideal conditions.

Perhaps I'm not getting your point?
 
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