Hi Andrew, fading of coloration can be from nutrients accumulation, resulting in a proportional increase of the zoox. density. A rapid change in water clarity will cause SPS bleaching, especially toward the top corals, ie. beginning carbon in a o/w non-carbon run system, or exchanging too much carbon quantities, beginning 03, etc. I've not noticed this phenomena in LPS but SPS can be adversely affected. Bob
Lets talk about lighting an SPS tank
- Thread starter JB NY
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, the increased clarity also increases photoilluminating color pigments within the coral tissue. Bob
ATJ
Premium Member
No-one wants to take on my challenge to guess the impact of water clarity on lighting in an aquarium!
My measurements show that the impact of water clarity on light transmission is not all that high. See: Light transmission in aquarium water: How important is water clarity?. I found that the loss in irradiance from air (and you aren't going to get water that clear) to yellowed old aquarium seawater was less than 20%. The increase in irradiance from the old seawater to air was less than 25%. The actual losses in a tank will be less because even with ozone and carbon you would not have water as clear as air.
A change in irradiance of 25% will cause no more than a 25% change in the gross photosynthetic rate. This is because the curve of photosynthesis versus irradiance is initially a straight line (at low irradiance). As irradiance increases, the rate of change in the photosynthetic rate decreases and so the impact of the change in irradiance could be much less. Such a small change in irradiance is likely to only cause a small change in the density of chlorophyll in the zooxanthellae. This will probably be too small to even be detectable as a change in colour of the coral.
An immediate increase of irradiance of 25% is not going to cause bleaching, unless the coral was already stressed. There have been numerous studies into photoacclimation in corals with increases in irradiance far larger than 25% and the colonies do not usually bleach. In one study, Stylophora pistillata colonies adapted to shade (10% of surface irradiance) were placed in full sunlight (100% of surface irradiance) and there was no bleaching. That's a 900% increase! Further, it would be difficult to cause an immediate increase in water clarity, other than doing a 100% water change and then it would be the water change that would cause the stress and bleaching.
An increase in zooxanthellae density due to elevated nutrients is unrelated to irradiance changes due to water clarity - although the two may coincide. Further, an increase in zooxanthellae would not cause the coral to fade but would make it darker. Certainly, it may become more brown and so appear less colourful, but that is not fading.
The function of coral pigments is not known. It has been suggested that fluorescent (GFP-like) pigments may be photoprotective and there is some evidence to support this. There is also conflicting evidence such as two colonies of the same species side by side receiving the same irradiance and one has GFP-like pigments and the other does not. If you assume that the GFP-like pigments are photoprotective, changes in irradiance may influence the density of the pigments. However, a change in irradiance of 25% is likely to have little impact on the coral and little need for a change in photoprotective pigments.
Pocilloporin (the pink pigment in pocilloporids) and the pocilloporin-like blue found in acroporids has been shown to not be photoprotective, UV protective nor photoenhancing and so there is no reason that changes in irradiance would make any difference to the density of these pigments.
What is a "photoilluminating color pigment"?
My measurements show that the impact of water clarity on light transmission is not all that high. See: Light transmission in aquarium water: How important is water clarity?. I found that the loss in irradiance from air (and you aren't going to get water that clear) to yellowed old aquarium seawater was less than 20%. The increase in irradiance from the old seawater to air was less than 25%. The actual losses in a tank will be less because even with ozone and carbon you would not have water as clear as air.
A change in irradiance of 25% will cause no more than a 25% change in the gross photosynthetic rate. This is because the curve of photosynthesis versus irradiance is initially a straight line (at low irradiance). As irradiance increases, the rate of change in the photosynthetic rate decreases and so the impact of the change in irradiance could be much less. Such a small change in irradiance is likely to only cause a small change in the density of chlorophyll in the zooxanthellae. This will probably be too small to even be detectable as a change in colour of the coral.
An immediate increase of irradiance of 25% is not going to cause bleaching, unless the coral was already stressed. There have been numerous studies into photoacclimation in corals with increases in irradiance far larger than 25% and the colonies do not usually bleach. In one study, Stylophora pistillata colonies adapted to shade (10% of surface irradiance) were placed in full sunlight (100% of surface irradiance) and there was no bleaching. That's a 900% increase! Further, it would be difficult to cause an immediate increase in water clarity, other than doing a 100% water change and then it would be the water change that would cause the stress and bleaching.
An increase in zooxanthellae density due to elevated nutrients is unrelated to irradiance changes due to water clarity - although the two may coincide. Further, an increase in zooxanthellae would not cause the coral to fade but would make it darker. Certainly, it may become more brown and so appear less colourful, but that is not fading.
The function of coral pigments is not known. It has been suggested that fluorescent (GFP-like) pigments may be photoprotective and there is some evidence to support this. There is also conflicting evidence such as two colonies of the same species side by side receiving the same irradiance and one has GFP-like pigments and the other does not. If you assume that the GFP-like pigments are photoprotective, changes in irradiance may influence the density of the pigments. However, a change in irradiance of 25% is likely to have little impact on the coral and little need for a change in photoprotective pigments.
Pocilloporin (the pink pigment in pocilloporids) and the pocilloporin-like blue found in acroporids has been shown to not be photoprotective, UV protective nor photoenhancing and so there is no reason that changes in irradiance would make any difference to the density of these pigments.
What is a "photoilluminating color pigment"?
ATJ
Premium Member
Joe,
I would have to assume that it is something that the carbon is taking out of the water or something that it is adding to the water that is stressing them.
Do they actually bleach (expel 50% or more of the zooxanthellae) or are we talking death of tissue?
How quickly after the addition of the carbon do they "bleach"?
I would have to assume that it is something that the carbon is taking out of the water or something that it is adding to the water that is stressing them.
Do they actually bleach (expel 50% or more of the zooxanthellae) or are we talking death of tissue?
How quickly after the addition of the carbon do they "bleach"?
JB NY
Active member
Hi Andrew,
No they bleach, most times they will recover their zoox in a few weeks. Normally one can notice the bleaching within a few days. But I have seen, both in my own tank and in others, bleaching associated with adding carbon. Most times it is when no carbon is used on the tank, then one day the person decides to add it and bleaches out their acros.
I'm also not sure I agree that a 25% increase in light will not cause bleaching, or that it is not significant. Going from a 250 watt SE Ushio 10K lamp to a 400 watt SE Ushio 10K lamp is about a 30% increase in light. I've seen many people bleach their corals going to the the higher 400 watt lamps.
No they bleach, most times they will recover their zoox in a few weeks. Normally one can notice the bleaching within a few days. But I have seen, both in my own tank and in others, bleaching associated with adding carbon. Most times it is when no carbon is used on the tank, then one day the person decides to add it and bleaches out their acros.
I'm also not sure I agree that a 25% increase in light will not cause bleaching, or that it is not significant. Going from a 250 watt SE Ushio 10K lamp to a 400 watt SE Ushio 10K lamp is about a 30% increase in light. I've seen many people bleach their corals going to the the higher 400 watt lamps.
ATJ
Premium Member
Joe,
Based on my measurements, I don't think you would get a 25% increase in irradiance just by using carbon. The difference from my old water to new water was only 13% and I think that is the most you could expect. Second, the increase is not going to happen immediately and will probably take a few days. That's plenty of time for a coral to photoacclimate to such a small change in irradiance.
Hoegh-Guldberg and Smith (1989) took colonies of Stylophora pistillata and Seriatopora hystrix which had been acclimated to 25% full sunlight and exposed them to 100% full sunlight. That's an increase of 300%. The colonies were much paler than they had been (and than the controls still at 25%) however the zooxanthellae density was unchanged. What had changed was a reduction in the chlorophyll content of the zooxanthellae. They also found that the expulsion rate of zooxanthellae in the exposed corals either did not increase or only increased slightly compared to the controls. Under the current definition of bleaching (loss of zooxanthellae) this would not be considered bleaching and is basically the zooxanthellae acclimating to the new conditions.
The change from 250W to 400W lamps could simply have been an increase in UVR which has been implicated in bleaching.
Hoegh-Guldberg O. and Smith G.J. 1989. The effect of sudden changes in temperature, light and salinity on the population density and export of zooxanthellae from the reef corals <i>Stylophora pistillata</i> Esper and <i>Seriatopora hystrix</i> Dana. <i>J. Exp. Mar. Biol. Ecol.</i>.<b>129</b>:279-303.
Based on my measurements, I don't think you would get a 25% increase in irradiance just by using carbon. The difference from my old water to new water was only 13% and I think that is the most you could expect. Second, the increase is not going to happen immediately and will probably take a few days. That's plenty of time for a coral to photoacclimate to such a small change in irradiance.
Hoegh-Guldberg and Smith (1989) took colonies of Stylophora pistillata and Seriatopora hystrix which had been acclimated to 25% full sunlight and exposed them to 100% full sunlight. That's an increase of 300%. The colonies were much paler than they had been (and than the controls still at 25%) however the zooxanthellae density was unchanged. What had changed was a reduction in the chlorophyll content of the zooxanthellae. They also found that the expulsion rate of zooxanthellae in the exposed corals either did not increase or only increased slightly compared to the controls. Under the current definition of bleaching (loss of zooxanthellae) this would not be considered bleaching and is basically the zooxanthellae acclimating to the new conditions.
The change from 250W to 400W lamps could simply have been an increase in UVR which has been implicated in bleaching.
Hoegh-Guldberg O. and Smith G.J. 1989. The effect of sudden changes in temperature, light and salinity on the population density and export of zooxanthellae from the reef corals <i>Stylophora pistillata</i> Esper and <i>Seriatopora hystrix</i> Dana. <i>J. Exp. Mar. Biol. Ecol.</i>.<b>129</b>:279-303.
ATJ
Premium Member
Joe,
I should add that I have frequently moved frags around in my tanks such that the irradiance they receive has increased significantly, sometimes more that double the previous irradiance. I've not had a frag bleach under those conditions. I am sure you would have made similar moves in your tank without incident and you have a quantum meter to see how much the irradiance has changed.
I should add that I have frequently moved frags around in my tanks such that the irradiance they receive has increased significantly, sometimes more that double the previous irradiance. I've not had a frag bleach under those conditions. I am sure you would have made similar moves in your tank without incident and you have a quantum meter to see how much the irradiance has changed.
measureing intensity on vho?
measureing intensity on vho?
I wonder here if you have taken into account that your intensity measurements were taken straight below the bulb on the halides, not taken into account the length of the vho bulb. The vho bulb spreads it's intensity out over a much larger area than the halide bulb does and I believe it would be hard to make an accurate estimate on intensity givin that fact.
measureing intensity on vho?
I wonder here if you have taken into account that your intensity measurements were taken straight below the bulb on the halides, not taken into account the length of the vho bulb. The vho bulb spreads it's intensity out over a much larger area than the halide bulb does and I believe it would be hard to make an accurate estimate on intensity givin that fact.
coralite said:
isnt that just what i said?
isnt that just what i said?
Yes under the halide would be higher par just like I just said which is also where the reading for par was taken. Go off to the side a couple feet and then take the reading for the halide and see what you get....less par!
isnt that just what i said?
Yes under the halide would be higher par just like I just said which is also where the reading for par was taken. Go off to the side a couple feet and then take the reading for the halide and see what you get....less par!
MiddletonMark
Premium Member
Chevell - hopefully coralite can reply - but it sounded like he was using a light meter to make those statements ... so it's hard to argue with the probe, you know?
Yet, spread on a VHO/etc is different from a MH [which IMO is very reflector-dependent for MH/point-source] - valid point
It's a good question hopefully he/others can share data on [as we can talk, but someone with said meter can just test it directly].
Yet, spread on a VHO/etc is different from a MH [which IMO is very reflector-dependent for MH/point-source] - valid point
It's a good question hopefully he/others can share data on [as we can talk, but someone with said meter can just test it directly].
soonerveebs
New member
Has anyone had a chance to see the Giesemann 13K bulbs? I need a bulb replacement, and I've heard good things but they come from those that sell them. Are they worth the extra money? I know JB hasn't had a chance to test it yet, but how is the color? I ask because the blueline 10K+ should be called a 20K-. Thanks.
Just a quick question. I set up a 65g tall (36*24*36....i mean 36*18*24) and I have one 250w DE 14KK Sun Aq bulb, which is a beatiful colour BTW. However, I am getting a second 250w DE because of the length of the tank. Since MH is a point source, I am getting great colouration but half of the corals are self-shading, so that on one side they are coloured, the other they are brown (like the moon...), I think this shows (at least to me) the potential for a t5 only tank or VHO supplementation. Do you think I should stick with 2 250W DE 14KK Sun Aq, or change the spectrum. My only worry is that I will provide too much light, not too little. I am mainly doing this for spread reasons and not for intensity reasons, I was thinking of upping to 20KK but that seems way to blue. I bought 2 t5 10k to put on my tank, and they don't exactly fit unfortunately, but I do want to keep the MH. Any suggestions?
Thanks,
Kev
Thanks,
Kev
NuclearReefs
Active member
kirei said:
keep the same kelvin and evenly space them perpedicular to the tank.. If it was a 4 foot tank i would suggest a 20K in the center, but Id stay with the 14K that way you dont have Light bands that will be apparent in your size tank..
Nathan
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