I borrowed an unopened Apogee MQ-500 quantum meter to test the PAR readings on both of my tanks. The metal halide bulbs on the 120 gallon are 9 months old and the T5's are and the bottom of the metal halide pendant is 9.75" above the water surface. The bulbs on the 80 gallon are 11 months old and the bottom of the Sunpower is 8.5" above the water surface.
Bulb combo: 2 Hamilton 20K & 2 ATI Actinic
Bulb combo: 4 ATI Blue Plus, 2 ATI Coral Plus & 2 ATI Actinic