Too much light?

[mckeec]

I recently upgraded my lights from 2x175 watt 10,000K MH to 2x400 watt 20,000K MH. I have had a recent rash of RTN and some have suggested my tank has too much light. This is on a 90 gal that is 24" tall and the lights are about 6"-8" above the water line. I could buy that the RTN is due to stress of the change in lighting, even though I did do a slow acclimation. But, could this really be TOO MUCH LIGHT? Everything I have read leads me to think not. What is your opinion?

 

[iCam]

Have you checked your water parameters, and temperature?

 

[mckeec]

Yes, water looks good and temp/pH/Ca/Alk have been steady. I have noticed that one of the bulbs does not look as bright and blue as the other. This bulb shows some black carbon charing at either end of the inner capsule of the bulb. It is a single ended XM. Could this be causing some odd light issues that may be related to the RTN. I have noticed on one of the acros, the tissue facing upwards to the light, has lightened some. My interpretation of it is like some kind of sunburn. How about UV protection. It is my understanding that this is built in on single ended bulbs and should not be an issue.

 

[iCam]

How , and for how long did you acclimate the tank to the new lighting?

My guess would be that it was brought on by the new lighting.

 

[mckeec]

I would agree that I suspect it is the new lighting. I did the layered screening thing where a layer is removed every few days. I guess what I am wondering is if it is the lights will it eventually stop as they will ultimitly get use to it.

 

[Malolo]

Going from 175s to 400s is a big step, but I can tell you your corals will benefit in the long run. You might try decreasing photoperiod during acclimation also.

 

[jmcmahon66]

When I upgraded from 175W to 250W I lost several corals to RTN. I thought I acclimated slowly, but obviously not slow enough. Most of my RTNs were on the upper 1/3 of my reefscape. I also had a mild temperature increase that probably didn't help. I would blame it on the lighting upgrade. 400W puts out a lot.
IME decreasing photoperiod was not as effective as window screen. HTH

 

[mckeec]

At this point I have completed what I thought was the acclimation. Would it be advisable to take a step backwards and reintroduce some screening and cut back the photo period, or would this just add to the stress at this time?

 

[stlouisguy]

No such thing as too much light, it just takes a bit of getting used to for the corals. Its like when the first real nice days of summer come and you go out and get burned.

 

[Malolo]

If you are seeing ongoing RTN I would back off. Have you had a lot of tissue loss or just pale areas developing? I have had coral bleach in response to added light and they recovered quite rapidly. Tissue loss is another story and needs to be addressed or you could lose the entire colonies.

 

[mckeec]

I have lost three whole colonies in about the past month. I think I will put some screening in place and cut back the photoperiod.

 

[organism]

how long do you have your lights on for?

 

[mckeec]

To tell you the truth, at this point I'm not sure. They have been on the same cycle that I set them up on over two years ago. I think I am running the MH for 10 hours, with actinic supplement at 12 hours.

 

[Greg 45]

For what its worth I have a 180 gal tank and run the lights 16inches over the top of tonk and only a 7 hour photo period. You can fry eggs with the 400 watt bulbs.
Good Luck

 

[organism]

I'd say the issue is with the higher lighting on the extended photoperiod, I'd cut that period at least in half for a little while to let them get used to things, I only ran my halides for 6 hours on my tank and it did amazingly well, the rest of the time was just actinic vho supplementation

 

[mckeec]

I will cut back the time and try running another series of screening. Thanks for the input.

 

[foob]

<a href=showthread.php?s=&postid=7168929#post7168929 target=_blank>Originally posted</a> by stlouisguy
No such thing as too much light, it just takes a bit of getting used to for the corals. Its like when the first real nice days of summer come and you go out and get burned.

Yes there is such a thing as too much light. This point is called photoinhibition, when the zooxanthellae's photosynthesis rate slows down or stops because there's too much light. Type photoinhibition on google and read away.

Of course to reach that point you probably need more light than that.

I believe it is the change that caused the RTN, not that you have too much light.