any idea what should my par be around to not BURN my corals?

[tdam]

Going to do a par check on my tank today. I just got an AI module a few weeks ago.

I hear about people burning their corals wit this light. so i was wondering, if anyone had a general idea on what my par should be to not burn my sps, Lps, softies?

 

[ichthyoid]

Timmy-

What is too much light varies by coral type. The term photoinhibition means an amount of light that causes a negative reaction from the coral.

I have read dozens of articles about this subject, and believe that the one below is one of the best I have found. Scroll down to the end of this article and look at Table #1, where data for different corals is listed.

http://www.advancedaquarist.com/2007/3/aafeature1">http://www.advancedaquarist.com/2007/3/aafeature1</a>

One thing that I have also read is that many corals will not react negatively at levels below ~500 PAR. Nor do many grow any faster at levels above ~300 PAR. So from this I would conclude that 300-500 PAR should be ok for most corals, although there will be exceptions.

Below is another article about too much light for a specific coral, but it is also very technical. I hope this helps.

[IMG]http://www.advancedaquarist.com/2004/7/aafeature">http://www.advancedaquarist.com/2004/7/aafeature</a>

 

[ichthyoid]

I should also mention that there are terms relating to the corals ability to use light-

Compensation point- the amount of light which allows the symbiotic algae (zooxanthellae) to produce enough energy to sustain the coral/keep it alive. This is the minimum level required.

Saturation point- the amount of light of maximum benefit to the coral. Any more light does not increase energy production.

Photoinhibition point- the amount of light which begins to negatively affect the coral. More is harmful.

 

[budsreef]

You also need to consider the level of lighting the corals were already getting under the previous fixture. The ideal thing would be to test the par before putting the new lights in but I know that isn't always practical.

 

[ichthyoid]

That is a great point Bud! The published numbers are maximum's. If a coral has been acclimated to lower levels and is placed under higher PAR levels it can be damaged, sort of like sunburn.

What happens is the zooxanthellae (symbiotic algae) in the coral either increase or decrease opposite to PAR level. So, more PAR less algae. The damage happens when there are lots of algae from low PAR and all of a sudden they get blasted with high PAR.

The algae produce a lot of food, but some toxins (peroxides) as well. If the coral can't eliminate those toxins fast enough, then the coral either shown signs of being burned, or worst case they expel the algae (bleach) in order to survive.