I was thinking about my 20 gallon tank problems and maybe the MH is to low. I was looking at these articles to learn more about MH. Most of the stuff confuses me, for example these graphs,
http://www.advancedaquarist.com/images/mar2004/fig19-giesemann-250-par.gif
but the other data seems like I would get a better spread by raising the pendants.
http://www.advancedaquarist.com/issues/mar2004/feature.htm
I don't know much about how spot lighting works. But my guess is that once the light hits the surface it goes straight down mostly. I think this, because the tank cast shadows and because I am having problems with growing the plants on the edges.
Normal Metal Halide Spread,
Metal Halide at 6" from surface,
Metal Halide at 12" from surface,
You can kind of see what I am talking about in this picture,
Greg
http://www.advancedaquarist.com/images/mar2004/fig19-giesemann-250-par.gif
but the other data seems like I would get a better spread by raising the pendants.
http://www.advancedaquarist.com/issues/mar2004/feature.htm
I don't know much about how spot lighting works. But my guess is that once the light hits the surface it goes straight down mostly. I think this, because the tank cast shadows and because I am having problems with growing the plants on the edges.
Normal Metal Halide Spread,

Metal Halide at 6" from surface,

Metal Halide at 12" from surface,

You can kind of see what I am talking about in this picture,

Greg