What would be considered high or very high lighting for a 20gal deep?
I have two 6500k bulbs on there now 20Watts ea 24" long.
Obviously you have two T12 bulbs over your tank. I am going to assume that you have about 2" of substrate and some sort of aluminum reflector behind the bulbs. If you have a 'standard 20H' (16.8" tall) I would estimate your PAR reading would be less than 30.......low light. If you have a 20XH (23.8" tall) I would estimate your PAR reading at less than 20.....low light.