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Re: Potassium and CF Lighting

Steve Dixon wrote:

>given my plants a very nice boost and vibrant growth, definitely one of the
>keys for improving my skill in the hobby.
>What is our current thinking on K?  Does the information I'm reporting
>square or conflict with your views and observations?  Thanks.

I observed the same increase in plant general health when I started adding
potassium in higher doses in my tank. My planted aquarium only begun to 
stabilize when I started adding KCl (and later K2SO4) in a dose twice as 
large as recommended in the PMDD recipe (to make up for the fact I don't 
add any KNO3). It was the main factor in achieveing a stable and healthy 

>Am I right in recalling that PAR ratings would give us a rating which would
>better correlate with plants general ability to use light than lumens?

Yes, IMO PAR should give a much better idea than lumens on how good a given
bulb is to feed photosynthesis.

>Does anyone have a definitive answer to this question?  Do CF bulbs put out
>more light per watt (lumen or PAR) than regular fluorescent bulbs; than T-8
>bulbs?  Do we have data on this point?

I have some data in http://www.aquabotanic.com/lightcompare.htm. The table
lists just one CF, the Osram Dulux L 55w/850. Its PAR/watt efficiency
factor is about 20% higher than equivalent (CRI ~ 80) but normal-output 
fluorescents. I have additional, non-published results for the Philips 
PL-L 55w/950, a higher CRI CF. Its PAR/watt factor is about 10% larger than 
other high CRI but normal output fluorescents (typically a C50 full spectrum
tube). I also have non-published results for the Philips TLD/950, a very 
high CRI full-spectrum T8 tube, that indicate its PAR/watt efficiency to 
be about 20% higher than normal full-spectrum fluorescents. Based on these 
very few but hard data points, I would say CFs and T8s are somewhat more 
efficient than normal output fluorescents.  

-Ivo Busko
 Baltimore, MD