thank you Diana, for your kind reply! I understand that lowering the water increases ir/uv light access to the plants, but I must admit I really enjoy the bubbles travelling up and having no visible watertable for the moment. I'll see how the plants do in the coming days and if growth is too slow, I'll lower the level as you suggest. (I completely believe you that it will make water changes easier : )
@hoppycalif, thanks for your reply as well!. My reasoning about your measurement is as follows: both uv and ir radiation get absorbed by glass. Even though the visible part of the spectrum may increase because of reflection, the useful part of the spectrum for plants decreases (rapidly) with higher watertable. Even if by total internal reflection both ir and uv radiation make it to the bottom, this will be only under a shallow angle, and will definitely be offset by the (dramatic) loss of radiation through water absorption. see http://www.koppglass.com/blog/optica...lass-interact/
Did you measure the total lux or the intensity of ir and uv separately? I'm interesting to hear what the distribution is of those wavelengths.