I realize that PAR and WPG cannot be directly correlated. One of the things I would like to know is that if a tank is, for example, a low(er) light tank at “2 WPG” what does that mean as far as a range of PAR values in µmol m^-2 s^-1? Or 1.5, 2.5, 3, ... WPG?

Also, what are reasonable PAR values for growing aquatic plants? (I realize that this is quite likely dependent upon the species of plant, but I would expect there is a median value ± a range).