Re: Lighting Intensity

     >I don't think that for a 30" tank, only the upper 14" would be 
     >illuminated, it's just that the amount of light at those levels are 
     >too low to support plant life.  I understand, too, that the blues are 
     >absorbed faster, hence the use of actinic tubes which are rich in 
     >blue to counter this loss.  Actinic tubes are in heavy use in marine 
     >reef tanks.
     Now, MY confusion alarm just went off.  First, plants can grow to a 
     water depth of 600' in nature; the 0-600' column is called the "photic 
     zone" by oceanographers, because the amount of light is enough to 
     support plants.
     RED light is absorbed first, followed by 
     orange-->yellow-->green-->blue.  Red light can penetrate as deep as 20 
     feet, in clear water.  If you are at 30 feet and you cut yourself, you 
     bleed dark GRAY.  It's very ethereal.
     The marine folks use actinic because the zooxanthellae within corals 
     use this particular wavelength.  This is the only reason.
     Oh, I have a 24" tank, and the E. tenellus at the bottom is doing just 
     fine.  It needs strong light, and I only have 4 40-watt NO tubes.