SPS bleaching where light doesn't touch it.

[rimlessreefpete]

So I have an interesting event happening in my tank. I have a bunch of sps corals that started out as frags and grew well and colored up real nicely. However over the past month and a half the bases have begun to bleach. I looked at every perameter and couldn't figure it out. One day I realized that the bleached parts are exactly where the upper branches are blocking the light from reaching the base and therefore bleaching it. The view from above looks perfect, everything is colored up and growing the way it should. Any Ideas.

Lighting is PAR38 LEDS should I add another one?
Increase Flow?
Any Ideas?

Perameters
Nitrates -0ppm
Phosphates-.04ppm
Magnesium -1350ppm
Calcium- 450ppm
Iodine-.06
alkalinity 10dkh
ph- 7.9

 

[jerpa]

You could supplement with additional PAR bulbs, although you will need wide optics unless you want to angle them. You could also add a few T5's or DIY some supplemental LED strips. I had the same problem with the Kessil 350. It seems to be a somewhat common problem with the spotlight style LED fixtures.

 

[rimlessreefpete]

It's a rimless tank so I have them mounted high enough where it spreads out and the spotlight effect is gone. I'll try adding another see if that helps. How did you overcome it?

 

[MHG]

All the SPS in my tank bleach and somewhat recess on the shadow side...

 

[DerekFF]

This is the fall out of pendant style fixtures. I had a conversation about this on my local reef club. I'll go find it.....brb

 

[jerpa]

When I ran the smaller kessils I supplemented with 2 T5 bulbs. I ended up switching back to halides after playing with the larger Kessils.

IMO the problem arises from the very small point source of light. No matter how high you raise the fixture the light is still being projected from a very small area when compared to "traditional" lighting.

 

[DerekFF]

http://forums.nvreefers.org/index.php?/topic/4502-Kessil-Lighting

Here is the discussion we had. IMO point source of light has been neglected to be a question raised by people about pendants. This discussion from my club is about Kessil but remains true about ANY pendant style fixture. Not just Kessil. T5 light can bend around corals and thus helps reduce the shadows and linear LED strips will also help reduce shadowing.

 

[ampemployee1]

I've had a coral grow frag grow into a 6" colony where the branches actually grow over itself like you described. The lack of light essentially kills that part of the coral being shadowed. I'm pretty sure this happens in nature too. If the coral is being shadowed by other corals, frag or reconsider coral placement. Sounds like you are seeing nice growth...

 

[a.browning]

I believe this is somewhat common, but definitely more likely with LEDs from what I've seen. Even with a 6-bulb ATI sunpower, some of my larger colonies will bleach out in the center, simply not enough light getting deep down in the branches. Make sure there is good flow through the colony so no detritus can accumulate on the branches and cause tissue loss, otherwise I wouldn't be too worried about it. You could add on couple of T5s to get some more coverage as others have suggested.

 

[DerekFF]

It does happen in nature, but nowhere near the extent you see in aquariums with pendant style LEDs. There is a post in my link that describes all the reflection of light in nature that does a superior job of preventing this for much longer.

 

[psykobowler]

That is why I added a bit of sand around the rock work. The light bounces back up so the shaded parts don't die.