Right well i took some rough and ready PAR readings and they do vary as might be expected with the t5s running doen the centre of the tank in only a 10" or so wide pendant.
Lighting regime at the moment is:
15:30 - 23:30 (8 hours) 216 watts Plant Pro
19:30 - 21:30 (2 hours) 432 watts Plant Pro + Osram 880
CO2
13:30 - 22:00 2x 5kg CO2
drop checker is light green.
Somewhat scary is the amount of PAR at 100% lighting, baring in mind these are 18" above the water and the tank itself is 28" deep.
216w:
So broadly speaking these are ranges of PAR, higher under the centre of the pendants lower towards the ends, lower still moving away from pendants front to back. Same goes at the substrate and is lowest in the corners around 23 at lowest. Over shadowed by a plant or hardscape it can go lower even in the brightest parts of the tank.
432w:
So yeah, Ouch! ET phone home. I am thinking as with the short 1-2 hours burst with Metal Halides with T5s some people do, this wont be too much of an issue as long co2 and nutrients are plenty.
Oh and I wont be making the mistake of my 2006 disaster aka Tank of Death. Ever since 00:00 to 12:00 O2 Pump on.