Are we GROSSLY OVERlighting?

I recently had a member of my local club come over with his quantum meter to check my PAR levels. I knew they would be decent even with all the salt stains on my reflectors that I haven't had time to clean!8) But thats a different story...
He did the test as I wrote the levels on a pic of the tank I took. I have 8 60" T5s on a 180, and a little more than half way down in the center I have a level of 428uMol/m2/sec, which I thought was good, and in the same center of the tank straight down to the sand I still had 270uMol/m2/sec, so 24" down I still had close to 300!! I was pleased with that to say the least. Granted the levels are different throughout the tank but he highest levels were obviously dead center.(I will post the levels, along with new pics of the tank in my tank thread shortly...)
In the bottom corners in the 6" off of the end of the 60" lamps I had 193 and 131uMol/m2/sec. I started to think about the other tests I have seen done on other members tanks, one guy I know Tom, had 500s on the bottom darn near of a 120 but he was cranking probably MORE watts on a small tank than I was. Granted I am only running 640 watts which is significantly less than 3 MH pendents most people would run on a 6' tank and then they would add supplementals.
I then thought of a couple of articles I read recently, one in TFH magazine by James Fatherree and one that it quotes a bit by Dana Riddle on Advanced Aquarists online.
Both articles are in regards to photosaturation(the most amount of PAR a coral can use for OPTIMUM growth) and photoINHIBITION(the level of PAR that actually is detrimentally to the coral, either starving it or bleaching it)
These articles helped me feel better about not cranking 700uMol/m2/sec all over my tank. In the articles it states that most corals even SPS grow great in the 200-300 range. Many of the SPS that people I know keep, have photosaturation points in the mid to upper 300's. So if they have them in areas of 600uMol/m2/sec all they doing is wasting light and money!
For example Acropora Millepora's saturation point is ~230uMol/m2/sec and Acropora Formosa's saturation point is ~340uMol/m2/sec. (Dana Riddle)
Needless to say, after taking my test, seeing how WELL my corals grow all in the range of 400s-190s I am GLAD I am not spending MORE money on the energy bill, I am also glad I can PROVE T5s CAN AND WILL grow SPS in a 180 all the way to the bottom!!

Happy reefing,debating and lighting!!

www.advancedaquarist.com/2007/3/aafeature1/view

 

wow...that was cool. I would be curious to see my light test results.
...also be able to monitor degradation of bulbs as they age.....what the heck is a quantum tester?.. OK GOOGLE time.......they cost a fortune I'll bet.
cool post doctor. : )
LG

 

So - short in all, us T5 users don't have to worry about placement up to 24" deep?
(i use x4 T5's)

I'd just like to add the my Duncans refuses to open its polyps at the top of my tank!

 

A quantum meter tests the level of photosynthetically available radiation or PAR values. PAR is what plants and corals use to grow....
An Apogee Quantum Meter cost about $275 or so..
A LUX meter would be a good way to check for bulb degradation as well.

Happy lighting

 

Yeah I have 270 in the dead center 24" down, capable of growing SPS rather quickly!! I have seen SPS grow in levels under 200uMol/m2/sec, James Fatherree showed some pics of SPS in levels of 100 or below, granted they were either browning out or growing slow, it is possible.
phoenix, what size tank do you have again, 90?

 

Advanced Aquarist's Online Magazine - Lateral Lines: Classification and Terminology For Reef Aquarium Lighting

heres a tank in germanyjust using T5, the site is translated.
Translated version of http://www.koralleninsel.at/gerhardw.html

there are some companies that keep there acro tanks with par between 250-350, my acro tank is 21" high and has a par between 350-450

http://www.advancedaquarist.com/2005/7/review

http://webtrolley.org/mivastore/merchant.mv?Screen=CTGY&Store_Code=apogee&Category_Code=BQM

 

I like it! One question: How fast is the degradation of PAR with age of bulbs? For example, are you losing 1/2 your intensity with 6 month old bulbs?

 

depends on the bulb

 

MH and PC degrade much faster than T5 but proper cooling also determines age of bulb as well...

Happy lighting!

 

Thanks for the answer, and that was a very informative post! I feel smarter already...