Hi or low light intensity

[madkeenreefer]

Considering photosaturation and not photoinhibition on Acropora.

High intensity light for shorter time periods or
Lower intensity light for longer periods. ( intensity refers to PAR.)

Does anyone have info on which one has benifits over the other or if there is any differences ?

 

[dzhuo]

1. High intensity light for shorter time periods or
2. Lower intensity light for longer periods. ( intensity refers to PAR.)

For photosaturation (or photoinhibition), #2 wouldn't matter. Photosaturation has nothing to do with length of photoperiod, it has everything to do with intensity. In other word, if the lighting source is intense enough, photosaturation (or photoinhibition) can happen almost instantly. If the lighting source is not intense enough, you can light the corals 24 hours and it would not reach photosaturation regardless.

If you are talking about which one is better (#1 or #2) then the answer can be very complicated and almost impossible to give a general answer.

Does anyone have info on which one has benifits over the other or if there is any differences ?

There is at least one research paper by Wang et al. in 2008 which looks at the affect of prolonged photoperiod and it's affect on the Clade B Symbiodinium (zooxanthellae). Since there is no standard definition of what's consider high-intensity or low-intensity, I don't know what exactly you might be interested.

 

[madkeenreefer]

For photosaturation (or photoinhibition), #2 wouldn't matter. Photosaturation has nothing to do with length of photoperiod, it has everything to do with intensity. In other word, if the lighting source is intense enough, photosaturation (or photoinhibition) can happen almost instantly. If the lighting source is not intense enough, you can light the corals 24 hours and it would not reach photosaturation regardless.

Thanks for the responce,
I guess I realy should have offered some PAr#'s here in my first post
so for argument sake
High intensity = 400-600 par
low intensity = 200-400 par
The photosaturation point is a point where the coral could usefuly use the light energy avalible and photoinhibition was were the coral could no longer effectivly use 100% of the light energy avalible.
Do the majority of acropora we keep not comence saturation at the 300+/- par range.?

If you are talking about which one is better (#1 or #2) then the answer can be very complicated and almost impossible to give a general answer.

If the light source was enought for the coral to effectivly capture and use
( lets say 200-400 par range) the lighting period could be longer
Par # are generalized for sake of discusion, although reflect my average lighting range
Still generalizing here but for aquarists who wish to veiw their tanks for longer periods like me, would it not be better to lets say "shoot" for # such as the lower intensity ones around 200-400 range ? (ps. I know very generalized here )

thanks again

 

[dzhuo]

High intensity = 400-600 par
low intensity = 200-400 par

That's very reasonable assuming 200 is above photo compensation while 600 is below photoinhibitation.

The photosaturation point is a point where the coral could usefuly use the light energy avalible and photoinhibition was were the coral could no longer effectivly use 100% of the light energy avalible.

You might be slightly confuse about photo compensation vs. photo saturation. Photo compensation is the point where the light is intense enough for photosynthesis to happen. Below this point, the light is useless for the coral. Photo saturation is the point where peak photosynthesis happens and beyond this point, more light would not yield more photosynthesis. Photoinhibitation is the point where the coral is starting to shut down to protect itself from lighting damage. It's not only the lights are not useful for photosynthesis, it's starting to hurt the coral. It's basically a condition you don't want to subject your corals to.

There is usually a large gap between photo saturation and photoinhibitation for most corals. This makes sense since most corals receive vary amount of light due to difference conditions and having a large gap before reaching photoinhibitation is clearly advantageous.

Do the majority of acropora we keep not comence saturation at the 300+/- par range.?

Yes for the data (only one) I have seen. Majority of corals (studies by Danna Riddle) peaks at ~300 (or below) so from a purely growing perspective, providing more light would not yield extra photosynthesis.

Still generalizing here but for aquarists who wish to veiw their tanks for longer periods like me, would it not be better to lets say "shoot" for # such as the lower intensity ones around 200-400 range ? (ps. I know very generalized here )

Yes I agree (generally speaking). However, there are clear evidence that longer period would harm the corals too although it's really hard to define exactly what's considered too long and the study I have seen is not typical for any aquarist. There is also the question whether multiple lighting cycle would be advantageous. For example, if one tank is light with 12 hours on and another 12 hours off while another is lighting it with 6 hours on, 6 hours off, another 6 hours on and off again. There is at least one paper suggest that the shorter cycle provides better grow.

 

[madkeenreefer]

You might be slightly confuse about photo compensation vs. photo saturation. Photo compensation is the point where the light is intense enough for photosynthesis to happen. Below this point, the light is useless for the coral. Photo saturation is the point where peak photosynthesis happens and beyond this point, more light would not yield more photosynthesis. Photoinhibitation is the point where the coral is starting to shut down to protect itself from lighting damage. It's not only the lights are not useful for photosynthesis, it's starting to hurt the coral. It's basically a condition you don't want to subject your corals to.

Thank you, you are correct, my statment should have read as;
The photo compensation not photosaturation point is a point where the coral could usefuly use the light energy avalible and photoinhibition was were the coral could no longer effectivly use 100% of the light energy avalible.

There is usually a large gap between photo saturation and photoinhibitation for most corals. This makes sense since most corals receive vary amount of light due to difference conditions and having a large gap before reaching photoinhibitation is clearly advantageous.

For the average guy such as myself, this point of photo saturation is it impossible to measure? How do I know how much light exposure is enought?

Yes for the data (only one) I have seen. Majority of corals (studies by Danna Riddle) peaks at ~300 (or below) so from a purely growing perspective, providing more light would not yield extra photosynthesis.

I am in the process of upgrading my lighting system and considering all the information avalible I am starting to assume that 250W will be fine to grow SPS in my tank. However by upgrading my lighting to 400w I will be able to keep corals lower in the tank around the 250par range and still have corals reciving 500+ par at the top end of the tank that will probly do just fine and not reach photoinhibitation, kind of hard to measure right?

Yes I agree (generally speaking). However, there are clear evidence that longer period would harm the corals too although it's really hard to define exactly what's considered too long and the study I have seen is not typical for any aquarist. There is also the question whether multiple lighting cycle would be advantageous. For example, if one tank is light with 12 hours on and another 12 hours off while another is lighting it with 6 hours on, 6 hours off, another 6 hours on and off again. There is at least one paper suggest that the shorter cycle provides better grow.

Seems interesting , do you have any first hand experiance with these lighting cycles ?

 

[chrisv]

I am in the process of upgrading my lighting system and considering all the information avalible I am starting to assume that 250W will be fine to grow SPS in my tank. However by upgrading my lighting to 400w I will be able to keep corals lower in the tank around the 250par range and still have corals reciving 500+ par at the top end of the tank that will probly do just fine and not reach photoinhibitation, kind of hard to measure right?

HA. Thrilled to see that this is a thread about MH lighting rather than another LED thread...

I am not sure that you will ever really reach photoinhibitation for shallow water small polyp stony corals using 400W metal halides. Without having any PAR numbers for reference I can tell you that the light at 12 ft depth on an equatorial reef makes our setups look downright dim.

Just aclimate things slowly.

 

[dzhuo]

For the average guy such as myself, this point of photo saturation is it impossible to measure? How do I know how much light exposure is enought?

Yes I would imagine it's hard to determine the photo saturation point for most average aquarists. For example, Danna's measurements were done using a PAM-210 (Teaching PAM) by Heinz Walz, Effeltrich, Germany. I have never seen one of such device and certainly do not have the knowledge to operate one. This device is used to measure both photo saturation and photoinhibitation but can't measure photo compensation point.

The other difficulty of measuring photo saturation is there is no standard and various different techniques have been used by different research groups.

I am in the process of upgrading my lighting system and considering all the information avalible I am starting to assume that 250W will be fine to grow SPS in my tank. However by upgrading my lighting to 400w I will be able to keep corals lower in the tank around the 250par range and still have corals reciving 500+ par at the top end of the tank that will probly do just fine and not reach photoinhibitation, kind of hard to measure right?

I think you are probably right. Photoinhibation is slightly easier to notice (not measure) because if a coral is subject to constant photoinhibitation, it will eventually bleach and starve or die. Also, photoinhibitation is not just a function of light. For example, flow has a tremendous affect on photoinhibitation as well. It's estimated that for certain corals, double the flow (in terms of velocity) can double the photoinhibitation as well. Other factors might play a role as well so it's something to think about.

Seems interesting , do you have any first hand experiance with these lighting cycles ?

I don't have any personal experience. I have always light my tank according to my viewing schedule; not optimal of grow.

 

[madkeenreefer]

HA. Thrilled to see that this is a thread about MH lighting rather than another LED thread...

I am not sure that you will ever really reach photoinhibitation for shallow water small polyp stony corals using 400W metal halides. Without having any PAR numbers for reference I can tell you that the light at 12 ft depth on an equatorial reef makes our setups look downright dim.

Just aclimate things slowly.

I agree to some extent to what you are saying , however I belive it is much to different of an environment for me to make a fair comparison between home aquaria and the open reef.

Thant being said it would be interesting to find out what the par #'s are that the people farming corals in ocean are averaging.

 

[dzhuo]

I am not sure that you will ever really reach photoinhibitation for shallow water small polyp stony corals using 400W metal halides.

Actually it's very possible to reach photoinhibitation even for shallow water SPS with today's lighting equipment. Some shallow water SPS have a relatively low photoinhibitation points such as mid 350 PAR. The myth seems to be that if a coral grows in shallow water, it must have a high photoinhibitation point which seems to be incorrect (at least from the studies we have found).

The real question is why such corals settle in shallow water when they can't possibly use the light available. No one has a definite answer to that yet. One guess is that the coral settle in shallow water by "mistake" base on the chemical cues from algae that grows between or under rocks which receive relatively little light. In another word, the corals are guided incorrectly.

Another popular believe why they settle in shadow water is that if the condition is hard for you, it's also going to be hard for your competitor. In other word, these corals settle in shadow water not because the condition is ideal but because it's NOT ideal for their competitors. There are lots of such examples in nature.

Generally speaking, most of us don't really have to worry about this sort of things because (like you said) corals are pretty adaptive so as long as you slowly introduce them to the new lighting, it's very possible they can accomodate a large range of lighting condition.

 

[chrisv]

I agree to some extent to what you are saying , however I belive it is much to different of an environment for me to make a fair comparison between home aquaria and the open reef.

Thant being said it would be interesting to find out what the par #'s are that the people farming corals in ocean are averaging.

I would also be very interested to hear about the strategies they use to color up corals. I wonder if, for example, ORA green house grown corals (a closed system i know) are brown when grown as a colony, but are then colored up under 20k halides before being shipped.

I dont think I have ever had a coral do poorly under a 14k 400W halide with actinic supplement. I wish I had a par meter to get a better idea what I am throwing at these guys...

I have certainly had corals lose color if I have moved them up too fast...but even then the normally color back up in about two months if my alkalinity is stable.

 

[chrisv]

Actually it's very possible to reach photoinhibitation even for shallow water SPS with today's lighting equipment. Some shallow water SPS have a relatively low photoinhibitation points such as mid 350 PAR. The myth seems to be that if a coral grows in shallow water, it must have a high photoinhibitation point which seems to be incorrect (at least from the studies we have found).

The real question is why such corals settle in shallow water when they can't possibly use the light available. No one has a definite answer to that yet. One guess is that the coral settle in shallow water by "mistake" base on the chemical cues from algae that grows between or under rocks which receive relatively little light. In another word, the corals are guided incorrectly.

Another popular believe why they settle in shadow water is that if the condition is hard for you, it's also going to be hard for your competitor. In other word, these corals settle in shadow water not because the condition is ideal but because it's NOT ideal for their competitors. There are lots of such examples in nature.

Generally speaking, most of us don't really have to worry about this sort of things because (like you said) corals are pretty adaptive so as long as you slowly introduce them to the new lighting, it's very possible they can accomodate a large range of lighting condition.

This is interesting information. Is it true that in the absence of competition, being below photoinhibitation is advantageous for the coral? Is it simply that they cannot use any more light to result in further growth advantage afte reaching photoinhibitation?

Do you work in this field or are you a hobbyist?

 

[dzhuo]

Is it true that in the absence of competition, being below photoinhibitation is advantageous for the coral?

I am not sure if anyone can conclusively say yes or no. I think the idea is that in the absence of competition, the coral would have greater access to other resources such as food (obviously light is just one factor) and space. It's basically a trade off. For example, the emperor penguins chose to breed in the harshest place on earth not because it's ideal as breeding ground but because there is almost no predators. It's a trade off having to endure a few months of extreme weather for the protection of the young. Lots of plants have evolve to take this evolution path as well: trading one resource for another and chose live in place whether competition is less intense.

Is it simply that they cannot use any more light to result in further growth advantage afte reaching photoinhibitation?

I don't understand this question but I probably don't have a definite answer anyway.

Do you work in this field or are you a hobbyist?

No. My work is not related to lighting or corals. I am just another hobbyist like the majority of us here.