Lets talk about lighting an SPS tank
- Thread starter JB NY
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goblinsharkman
New member
OMG, you guys are awsome...hi im ben im new to this forum on RC, im starting a science fair project at my school, compairing coral growth to light intesity and color tempature. You guys provivded so much info, it think this link plus the works of Steve Tyree, Sanjay Joshi, and Dana Riddle will be my bibleography, i will most likley have some questions for you SPS buffs later on in my expieriment... THANK YOU
NuclearReefs
Active member
Dana is a great guy,, I used to hang out with him a bit when i lived in atlanta,, we did alot of lighting test and some water flow test on the show tank at the store I managed,,, we had probably the highest FPS surge tested at the time,,, LOL,, 8 fps ,, we had a 55 gallon and 2 35 gallon surges in the corner of a 265 gallon tank ,,LOL! Sanjay and steve have written some awsome stuff too.. I wish Id gotten into this when I was in school,,,,,,
ATJ
Premium Member
Joe,JB NY said:
You have it back to front. VHO and other fluorescent lamps have a wide spread of light - along the whole length of the tube - and because of this (which I will explain below) the light actually penetrates much more deeply. A metal halide lamp is a point source and so there is a much quicker drop off in intensity with distance.
The problem with fluorescent lamps is not penetration (and light is light and has the same characteristics regardless of how it is created). Rather, it is that the total light output of the lamp is spread over the entire length of the lamp resulting in a much lower starting intensity at any one point along the length of the lamp.
All other factors being equal, a point light source is subject to the inverse square rule. If you double the distance from the light source, the intensity will be one quarter. i.e. there will be 4 times as much light at 15" than there will be at 30" from the lamp.
This diagram from one of my RK articles demonstrates the inverse square rule:
As a fluorescent lamp puts light out along the whole length, it is analogous to a line of point light sources. While each of those point sources are subject to the inverse square rule, the light from each overlaps with adjacent points such that much of the drop off in intensity with distance is accommodated by more light intersecting the theoretical point source.
My own readings both in air (Light Intensity) and in my tanks, back this up. In fact, in one of my tanks which is lit by 4 NO fluorescent tubes, I get higher PAR midway down the tank than I get close to the surface.
NuclearReefs
Active member
trevor,, so your testing with MH bulbs .. What kinda reflectors /bulb arrangement were you using? Vertical mounted bulbs? Horizontal? The types of reflectors that have been made available since your 2000 test have increased alot in quality...
Id be interested in seeing what kinda PAR readings you would get on the new DE bulbs that are on the market. especiallly the iwasaki's.
Nathan
Id be interested in seeing what kinda PAR readings you would get on the new DE bulbs that are on the market. especiallly the iwasaki's.
Nathan
ATJ
Premium Member
Nathan,
I think you misunderstood the point of my post. I was not commenting on the light output of a metal halide lamp versus a fluorescent lamp, but rather the physics that governs the behaviour of the light they radiate. The inverse square rule will apply no matter at what colour temperature the lamp is rated. Similarly, orientation of the lamp or the construction of the reflector will only have a minor influence. It also won't matter if it is a 150W or a 400W MH lamp, the same principles apply.
Quoting PAR for any light source is actually quite meaningless unless you define the conditions under which it was measured, such as the distance from the lamp. It would be like going to the hardware store and asking for 2" of sand. Similarly, comparing the PAR readings from one lamp, or fitting, to another only has meaning if all other parameters are equal.
I think you misunderstood the point of my post. I was not commenting on the light output of a metal halide lamp versus a fluorescent lamp, but rather the physics that governs the behaviour of the light they radiate. The inverse square rule will apply no matter at what colour temperature the lamp is rated. Similarly, orientation of the lamp or the construction of the reflector will only have a minor influence. It also won't matter if it is a 150W or a 400W MH lamp, the same principles apply.
Quoting PAR for any light source is actually quite meaningless unless you define the conditions under which it was measured, such as the distance from the lamp. It would be like going to the hardware store and asking for 2" of sand. Similarly, comparing the PAR readings from one lamp, or fitting, to another only has meaning if all other parameters are equal.
JB NY
Active member
Hi Andrew,
That some great stuff I didn't know you did that.
Your right. I meant the long length of the tube allow the light to be spread out lengthwise but not as much from the sides.
I still think MH win in a few areas for overall light intensity. The light spread of a MH lamp when used in a reflector (I know you didn't test that, but most people use a reflector) is about a 2 foot by 2 foot area, much larger I think than a single VHO lamp will produce good light.
I think when a VHO lamp puts out light from the sides, it's not as intense as the center of the tube going lengthwise. Also the output is not exactly the same per watt. Looking at your data, at the bottom of an aquarium aprox. 50cm the light output with the NO is about 19 PPFD while the 150 watt MH is about 100. Even if you put a 140 watt VHO I would assume the output would go up about 3.5 times. So the 19 PPFD would go up to 66.5, still much lower than the MH, even with their output about the same. Also adding a good reflector to the MH can almost double (sometimes more) the output from the lamp.
But you bring up a good point, and it shows why some people are able to get some nice coloration with acroporids in a tank lit with VHO only.
That some great stuff I didn't know you did that.
ATJ said:
Your right. I meant the long length of the tube allow the light to be spread out lengthwise but not as much from the sides.
I still think MH win in a few areas for overall light intensity. The light spread of a MH lamp when used in a reflector (I know you didn't test that, but most people use a reflector) is about a 2 foot by 2 foot area, much larger I think than a single VHO lamp will produce good light.
I think when a VHO lamp puts out light from the sides, it's not as intense as the center of the tube going lengthwise. Also the output is not exactly the same per watt. Looking at your data, at the bottom of an aquarium aprox. 50cm the light output with the NO is about 19 PPFD while the 150 watt MH is about 100. Even if you put a 140 watt VHO I would assume the output would go up about 3.5 times. So the 19 PPFD would go up to 66.5, still much lower than the MH, even with their output about the same. Also adding a good reflector to the MH can almost double (sometimes more) the output from the lamp.
But you bring up a good point, and it shows why some people are able to get some nice coloration with acroporids in a tank lit with VHO only.
NuclearReefs
Active member
Well,, I have actually cut the time on my halide back to 4 hours a day,, and I can tell a difference allready in some of my more delicate pieces,, they are coloring a little better i think personally
ATJ
Premium Member
Joe,
I still think MH win in a few areas for overall light intensity. The light spread of a MH lamp when used in a reflector (I know you didn't test that, but most people use a reflector) is about a 2 foot by 2 foot area, much larger I think than a single VHO lamp will produce good light.
I agree! Using a metal halide lamp will generally result in much higher intensities directly under the lamp than would be possible with the equivalent light output from a fluorescent lamp.
I did actually use a reflector. There is a link on that page to a picture of it. I just wasn't testing the efficiency of a reflector. Unless the reflector is a perfect parabola, with the lamp at the perfect focus, the inverse square rule will apply. Even if the reflector was parabolic, the inverse square rule would apply to the light that was coming straight from the lamp and not hitting the reflector. This could be as much as 50%.
The coverage of the metal halide lamp will also vary with distance and would be dependant on the reflector, but, yes, in general it will cover an area of 2' by 2'.
I think when a VHO lamp puts out light from the sides, it's not as intense as the center of the tube going lengthwise. Also the output is not exactly the same per watt. Looking at your data, at the bottom of an aquarium aprox. 50cm the light output with the NO is about 19 PPFD while the 150 watt MH is about 100. Even if you put a 140 watt VHO I would assume the output would go up about 3.5 times. So the 19 PPFD would go up to 66.5, still much lower than the MH, even with their output about the same. Also adding a good reflector to the MH can almost double (sometimes more) the output from the lamp.
Yes, the output in the centre of a fluorescent tube is generally greater in the middle of the tube than the ends. Additionally, the closer you get to the ends, the fewer adjacent theoretical point sources there would be and so the light would drop off even more quickly.
But you bring up a good point, and it shows why some people are able to get some nice coloration with acroporids in a tank lit with VHO only.
Fluorescent lighting (whether it be NO, VHO and to a large extent PC) will result in more uniform lighting both horizontally and vertically. The intensity in the brightest areas will not be a lot brighter than the intensity in the darker areas. In a tank lit with metal halide lamps, there will be much greater variation in intensity throughout the tank. High up, directly under the lamps will be much brighter than low down away from the centre of the lamps. Metal halide lighting will generally work much better for a tank with mixed species as you are able to place colonies in more appropriate places based on their light requirements. Of course, many (most?) corals are pretty flexible when it comes to light requirements, so it may not be such a big advantage, but never-the-less, it is a good advantage to have.
I still think MH win in a few areas for overall light intensity. The light spread of a MH lamp when used in a reflector (I know you didn't test that, but most people use a reflector) is about a 2 foot by 2 foot area, much larger I think than a single VHO lamp will produce good light.
I agree! Using a metal halide lamp will generally result in much higher intensities directly under the lamp than would be possible with the equivalent light output from a fluorescent lamp.
I did actually use a reflector. There is a link on that page to a picture of it. I just wasn't testing the efficiency of a reflector. Unless the reflector is a perfect parabola, with the lamp at the perfect focus, the inverse square rule will apply. Even if the reflector was parabolic, the inverse square rule would apply to the light that was coming straight from the lamp and not hitting the reflector. This could be as much as 50%.
The coverage of the metal halide lamp will also vary with distance and would be dependant on the reflector, but, yes, in general it will cover an area of 2' by 2'.
I think when a VHO lamp puts out light from the sides, it's not as intense as the center of the tube going lengthwise. Also the output is not exactly the same per watt. Looking at your data, at the bottom of an aquarium aprox. 50cm the light output with the NO is about 19 PPFD while the 150 watt MH is about 100. Even if you put a 140 watt VHO I would assume the output would go up about 3.5 times. So the 19 PPFD would go up to 66.5, still much lower than the MH, even with their output about the same. Also adding a good reflector to the MH can almost double (sometimes more) the output from the lamp.
Yes, the output in the centre of a fluorescent tube is generally greater in the middle of the tube than the ends. Additionally, the closer you get to the ends, the fewer adjacent theoretical point sources there would be and so the light would drop off even more quickly.
But you bring up a good point, and it shows why some people are able to get some nice coloration with acroporids in a tank lit with VHO only.
Fluorescent lighting (whether it be NO, VHO and to a large extent PC) will result in more uniform lighting both horizontally and vertically. The intensity in the brightest areas will not be a lot brighter than the intensity in the darker areas. In a tank lit with metal halide lamps, there will be much greater variation in intensity throughout the tank. High up, directly under the lamps will be much brighter than low down away from the centre of the lamps. Metal halide lighting will generally work much better for a tank with mixed species as you are able to place colonies in more appropriate places based on their light requirements. Of course, many (most?) corals are pretty flexible when it comes to light requirements, so it may not be such a big advantage, but never-the-less, it is a good advantage to have.
ATJ
Premium Member
Joe,JB NY said:
It is important to understand that these are the peak irradiance levels and are not maintained for the whole day. While the peak irradiance has some importance, the total PAR received over the course of a day or even days, weeks and months is far more important. It is this that determines whether photosynthesis exceeds respiration.
The peak irradiance at a certain location may be 600 μE.m<sup>-2</sup>s<sup>-1</sup> at 15 m. However, for the full day the PAR may be 14-15 E.m<sup>-2</sup>. In our aquaria, irradiance is fairly constant for the whole day (when the lights are on), so that if you were to run your lights for 10 hours per day, you would only need around 420 μE.m<sup>-2</sup>s<sup>-1</sup> to provide the equivalent amount of light. So the 200-600 μE.m<sup>-2</sup>s<sup>-1</sup> peak, becomes 140-420 μE.m<sup>-2</sup>s<sup>-1</sup> average over 10 hours.
The other thing to consider is the time of the year those peak irradiances were measured. If they were taken close to the Summer solstice, the peak irradiance at the Winter solstice may be little more than half that value at the same depth.
JB NY
Active member
Good point on the average values being lower from the peak that are stated.
Have you found much on light levels on actual reefs hosting acroporids? I had a hard time coming up with much. I've been feeling that we actually have light levels in our tanks that exceed what these corals experience on a daily basis. I know that in my tank, I've got to be careful in the upper 1/4 of the tank as some acros can get too washed out looking, or even bleach. I've had good luck in the middle and even on the bottom of my tank (tank bottom has a reading of around 200 PAR).
Have you found much on light levels on actual reefs hosting acroporids? I had a hard time coming up with much. I've been feeling that we actually have light levels in our tanks that exceed what these corals experience on a daily basis. I know that in my tank, I've got to be careful in the upper 1/4 of the tank as some acros can get too washed out looking, or even bleach. I've had good luck in the middle and even on the bottom of my tank (tank bottom has a reading of around 200 PAR).
ATJ
Premium Member
Joe,
At the moment I only have one set of light readings taken at the surface during one day at One Tree Island (southern Great Barrier Reef). I am trying to get more.
I have been playing with some calculations that I believe give a pretty good approximation of the PAR at certain depths. The calculations take into account the latitude/longitude of the site, time of day, time of the year as well as depth.
The following is my estimation for 21 December (Summer solstice) for Heron Island:
It assumes perfectly clear skys with very low humidity and clear water.
The same for 21 June (Winter solstice):
I believe I am overstating the PAR in my calculations and I am assuming perfect conditions. I think the reality will be less than this.
I agree on exceeding light levels - unless people are keeping intertidal species that get exposed to full sun. Also, it has been shown that even natural conditions there is actually too much light for the corals and they photoinhibit. It is likely that many of the colours that people desire are the result photoprotective pigments - at least that's where most of the research is pointing.
I only have 150W metal halides on my Reef tanks (18" high) and my corals all do well - even on the bottom. Only in the corners do they appear to get insufficient light.
At the moment I only have one set of light readings taken at the surface during one day at One Tree Island (southern Great Barrier Reef). I am trying to get more.
I have been playing with some calculations that I believe give a pretty good approximation of the PAR at certain depths. The calculations take into account the latitude/longitude of the site, time of day, time of the year as well as depth.
The following is my estimation for 21 December (Summer solstice) for Heron Island:
It assumes perfectly clear skys with very low humidity and clear water.
The same for 21 June (Winter solstice):
I believe I am overstating the PAR in my calculations and I am assuming perfect conditions. I think the reality will be less than this.
I agree on exceeding light levels - unless people are keeping intertidal species that get exposed to full sun. Also, it has been shown that even natural conditions there is actually too much light for the corals and they photoinhibit. It is likely that many of the colours that people desire are the result photoprotective pigments - at least that's where most of the research is pointing.
I only have 150W metal halides on my Reef tanks (18" high) and my corals all do well - even on the bottom. Only in the corners do they appear to get insufficient light.
I am assuming the vertcal axis is PAR and the horizontal axis is time of day, correct? I have also started to wonder if people have been going overboard on lighting. Like anything in this hobby(or life) it seems people go to extremes(especially with sps tanks)and then things settle down somewhere in the middle. Thanks to both JBNY and ATJ for the info
Chris
Chris
NuclearReefs
Active member
Yep Fishdoc,,, I believe they are.. So what im getting from this is the peak PAR periods are only about 4 hours ,, so we are cooking corals....
I cut my halides back to 5 hours about 2 weeks ago and Im actually starting to see more growth....Tips of all my pieces seem to be showing new branches as well. I think this is a result of reduction of the UV Exposure.
Andrew Im with you a 100% on the coloring of corals being a defense mechanism as photoprotective pigments. Dana and I have talked about this some . The one thing most people fail to realize is these corals are not all bright colors in the wild. The Acroporids Ive seen at 6-15 meters were mostly darker colors,browns,reds, etc,,,,
Nathan
I cut my halides back to 5 hours about 2 weeks ago and Im actually starting to see more growth....Tips of all my pieces seem to be showing new branches as well. I think this is a result of reduction of the UV Exposure.
Andrew Im with you a 100% on the coloring of corals being a defense mechanism as photoprotective pigments. Dana and I have talked about this some . The one thing most people fail to realize is these corals are not all bright colors in the wild. The Acroporids Ive seen at 6-15 meters were mostly darker colors,browns,reds, etc,,,,
Nathan
Mchava
Active member
i too have wonder that becuase the highest peak happen when the sunns i in its highest point which only last up to about 4-5hours a day. I i have set me light that way. Here is my lighting period(custom to my time but simulate the day:
Attinics 11am
150mh Saki ON 1pm
2x175 mh ON 3pm (highest point)
2x175mh OFF 7pm
150 Saki OFF 9pm
moonlights ON 10pm
Atinics OFF 11pm
moonlights OFF 12pm
With this combo I get a full 12hours photoperoid to simulate the day. So what you guy think?
Attinics 11am
150mh Saki ON 1pm
2x175 mh ON 3pm (highest point)
2x175mh OFF 7pm
150 Saki OFF 9pm
moonlights ON 10pm
Atinics OFF 11pm
moonlights OFF 12pm
With this combo I get a full 12hours photoperoid to simulate the day. So what you guy think?
jauringer
Premium Member
Remote DATA Station on the GBR
JB, Are you looking for somthing like this. Here is a list of Remote data stations on the GBR. I have spoken with one of the DR.s in charge over there. The light meter is 10m obove the surface of the water. This will give your daily reading in 30min intervals and yearly averages for specefic reefs. You can even go a step further and reed about the specefic corals in each area.
Jason
JB, Are you looking for somthing like this. Here is a list of Remote data stations on the GBR. I have spoken with one of the DR.s in charge over there. The light meter is 10m obove the surface of the water. This will give your daily reading in 30min intervals and yearly averages for specefic reefs. You can even go a step further and reed about the specefic corals in each area.
Jason
ATJ
Premium Member
Chris,
Fixed.
Nathan,
It really depends on your definition of "peak". PAR will be at it's highest for only a few seconds on any one day, but if "peak" includes within 10% of the highest value, yes, about 4 hours.
I guess I wouldn't go so far as say "cooking", but I think they are getting far more light than they need. It has been shown that corals in shallow water actually shutdown photosynthesis as early as 9am and may not start up again until late in the afternoon.
My opinion on corals in shallow water is that they tolerate the conditions there rather than require the conditions. Evolution favours the selection of characteristics and adaptations that allow an organism to better survive in an environment and out compete other organisms for resources. On a coral reef, space is a extremely important resource and I believe that intertidal corals have evolved the ability to tolerate the extremes of intertidal habitats so they can colonise those areas. They may still survive and thrive in deeper water with less water movement, but they will also have more competition.
Jason,
That might be some good data with which I can verify my calculations - at least for surface PAR. I just have to find some of the data that has been populated. Unfortunately, they don't have any underwater readings.
Fixed.
Nathan,
It really depends on your definition of "peak". PAR will be at it's highest for only a few seconds on any one day, but if "peak" includes within 10% of the highest value, yes, about 4 hours.
I guess I wouldn't go so far as say "cooking", but I think they are getting far more light than they need. It has been shown that corals in shallow water actually shutdown photosynthesis as early as 9am and may not start up again until late in the afternoon.
My opinion on corals in shallow water is that they tolerate the conditions there rather than require the conditions. Evolution favours the selection of characteristics and adaptations that allow an organism to better survive in an environment and out compete other organisms for resources. On a coral reef, space is a extremely important resource and I believe that intertidal corals have evolved the ability to tolerate the extremes of intertidal habitats so they can colonise those areas. They may still survive and thrive in deeper water with less water movement, but they will also have more competition.
Jason,
That might be some good data with which I can verify my calculations - at least for surface PAR. I just have to find some of the data that has been populated. Unfortunately, they don't have any underwater readings.
NuclearReefs
Active member
thanks andrew,, very insightfull,, so we shall see how my sps like being relaxed with a shorter photoperiod.. I have stepped mine down an hour a week so far.... I was buring my halides at 8 hours,, Im down to 6 now.
Nathan
Nathan
Mchava
Active member
hey nuclear nice tank. Are u using any kind of calcium reactor? If not what are u using. I also have a 40 breeder but don't have the color like you do. I have great growth but no color on some of my corals. On a side note I like your halloween pictures in your site. especialy this one http://img54.photobucket.com/albums...=view¤t=HALLOWEEN_FLASH_WITH_TEXT_1.jpg
ATJ
Premium Member
Nathan,
Generally, longer periods with lower intensity will be better for the health of the coral than short periods of higher intensity.
If you look at the relationship between irradiance and photosynthesis, the curve is steeper at lower irrandiance levels:
Using the arbitary units above, 8 hours at 250 will result in significantly more photosynthesis than 4 hours at 500. Of course, in reality, the coral and its zoxanthellae will photoacclimate and so the differences may not be all that great, but the trend will still be there. Additionally, if the high intensity is such that it causes photoinhibition, the coral may not get enough energy.
I also meant to respond to your comments about acroporids in 6-15 metres. My observations have been quite different and I have seen some fabulous colours even deeper than 15 metres.
See:
Dive at Admiralty Anchor, Osprey Reef, Coral Sea on 1/09/2003
Dive at London Fog Bommie, Osprey Reef, Coral Sea on 1/09/2003
And if you look at some of my other dives, there are quite a few colourful acroporids at depth.
Generally, longer periods with lower intensity will be better for the health of the coral than short periods of higher intensity.
If you look at the relationship between irradiance and photosynthesis, the curve is steeper at lower irrandiance levels:
Using the arbitary units above, 8 hours at 250 will result in significantly more photosynthesis than 4 hours at 500. Of course, in reality, the coral and its zoxanthellae will photoacclimate and so the differences may not be all that great, but the trend will still be there. Additionally, if the high intensity is such that it causes photoinhibition, the coral may not get enough energy.
I also meant to respond to your comments about acroporids in 6-15 metres. My observations have been quite different and I have seen some fabulous colours even deeper than 15 metres.
See:
Dive at Admiralty Anchor, Osprey Reef, Coral Sea on 1/09/2003
Dive at London Fog Bommie, Osprey Reef, Coral Sea on 1/09/2003
And if you look at some of my other dives, there are quite a few colourful acroporids at depth.
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