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Acropora & LED lights


uglyfish

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I'm getting nice coloration on various SPS (acros and montis), but only where they get DIRECT exposure to LED light. When you look at them from the top, they look bright and colorful, but the sides and shadow areas are dull and brown.

 

Is this because the LED light isn't diffused enough? Or do I just need to give it more time and the sides will colour up eventually? Is it a water quality issue?

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Bongo Shrimp

This will happen with pretty much any lighting. Acros are usually best viewed from the top down and always look different from the side. Even my friend who has two 400w MHs over his tank experiences this phenomenon. Maybe slightly less noticeable in his tank however thats just how it works. The zooxanthellae grow where there is the optimum exposure to light.

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jedimasterben
This will happen with pretty much any lighting. Acros are usually best viewed from the top down and always look different from the side. Even my friend who has two 400w MHs over his tank experiences this phenomenon. Maybe slightly less noticeable in his tank however thats just how it works. The zooxanthellae grow where there is the optimum exposure to light.

Hit the nail on the head, only problem with your reply is that zooxanthellae are brown - the coral itself is colorful. Where light is strongest, there are less zooxanthellae, so the coral's colorful shield is able to be seen more. :)

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Bongo Shrimp
Hit the nail on the head, only problem with your reply is that zooxanthellae are brown - the coral itself is colorful. Where light is strongest, there are less zooxanthellae, so the coral's colorful shield is able to be seen more. :)

 

No, they are only brown if they become over populated. At the right density/population they appear to have a color.

 

The resulting color change of a coral in response to different light intensities is due to the concentration of both the zooxanthellae cells and the amount of chlorophyll present within those cells. The color of these cells ranges from a golden-yellow to brown. The higher the concentration of these cells within the coral, the more the coral will take on a brown appearance. In other words, if the lighting is less intense than the coral is accustomed to, it will take on a darker brown appearance. On the other hand, when the same coral is placed under intense lighting, some of the zooxanthellae cells will be expelled and the amount of chlorophyll reduced, giving the coral a lighter appearance.

 

From: http://www.peteducation.com/article.cfm?c=...67&aid=2693

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jedimasterben
Buy why does have to be so painful :D

I though zooanthellae cam in other colors and coral has no color? :huh:

Not quite - zooxanthellae absorb certain spectrums of colors and reflect back what they don't use. Most photosynthetic pigments (such as chlorophyll) absorb two primary spectrums, see here in this photo for an example:

pigment.gif

 

Now, the spectrums they don't make full use of are reflected back, so chlorophyll a gets you a green color, peridinin gets you a brick red color. Problem being that zooxanthellae do not use only one photosynthetic pigment, using two or more. Peridinin is absolutely required for chlorophyll a to function, so they are always present together, and when you mix green and brick red, you get.... brown! Woo hoo! ;)

 

Here is a nifty chart I grabbed from the Youtube video I post below:

Untitled-1-1.jpg

 

 

Now, coral coloration is actually a defense against being hit with too much light, whether it could be used for photosynthesis or not. For instance, you can blast a green coral with blue light all day long, but introduce too much green or red light into the mix and it can cause damage to the coral because it doesn't have any defense against these new spectrums and can take in too much light.

 

What's really interesting is that if a coral, say, absorbs green light and reflects blue light, the blue light can actually be caught by the zooxanthellae and used for photosynthesis!

 

Watch this video, from 21:52, and it will explain better than I can. :)http://www.youtube.com/watch?v=g3vdfkqOLtU

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You could drop your lights closer to the surface to help the lights hit the undersides and reduce shadowing. Its one of the changes i made in redoing my diy fixture. I removed the 60 degree optics and dropped the light from 12 inches to 3.

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jedimasterben

Unless you have a tank that is less than the width of the fixture, it won't really happen that way. You would actually need the LEDs to be spread out and possibly tilted inward to have that happen.

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  • 1 month later...

Still fighting the color problems. Dropped the lights to 5" off water.

See pics:

 

Nice colour from top...

20121006172643.jpg

 

Blahhhh from the side...

20121006172709.jpg

 

Is this just me?

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