PAR reading help

[mperales]

Hello and thanks in advance for any help you may give. I recently borrowed a PAR meter (Sun System) from my LFS. Currently I have a 75 Gal mix reef with two Radions 8 inches from the top of the water. The lights have been slowly and progressively been ramped up. Started at 50% and increased 5% weekly to the current 80% brightness (maximum 3 hour period at 100% full spectrum). My concern is that one of the Acropora has grown very close to the top of the water. The PAR reading here averages 550 (average of 3 readings) Is that too strong? The coral has actually colored up but it has only been at 80% for 1 week.

This is a picture of the tank with the PAR readings in red



At sand level, left to right (Crocea clam [130], Favia [170], Plate coral [120], open brain [130] and Lobo [225] to the right.
So, is the 550 PAR reading too strong for the Acro?

Thanks,

 

[drw94]

I think you are find as long as the coral is looking good and is healthy. Corals in my experience can handle a ton of light if they are acclimated to it. If everything in you tank is growing I would keep the lights the way they are. Hope this helps.

 

[sahin]

I currently use a modified ATI Sunpower which has T5's and LED's.

I also have my own Apogee PAR Quantum meter.

I'd say keep a close eye on the coral at the top. If it shows signs of lightening/bleaching then you either need to move it lower or reduce the intensity or length of time the max intensity is on for.

If it has been acclimated well to the light, it might be ok. Maybe take a photo at a known setting on camera and light, and then take another photo a week later with exactly the same conditions and see if it has lightened up?

 

[tomservo]

It can depend highly on the species whether or not that's too much light. There was mention in the AA article (http://www.advancedaquarist.com/2012/12/corals) that more light isn't always the key to better color. One coral (green slimer?) got better color all the way to 900 PAR, where it levelled off, and another lost color past 200 PAR.