Hmm.. interesting.
'Intensity'? how to judge that?
'Super clean' tank? how clean is super clean?
Well.. in conclusion. none can compare that the natural sunlight. And 2 hours, i dont think it works, as our tank is not super clean and not as intensified as the SUN. I wouldnt want to risk losing colours just for 2 hours duration of MH photoperiod.
Just to mention a case, I normally run my 400watter under 6hrs. all my sps colours change and turned to brown even with NO3 and PO4 measured zero. But after adjusting to 10hrs, the colours not only recover to the norm but quite intensed. I realised that when i adjust to 8hrs. Now back to 10hrs.
Again, this also depends on many parameters and also the 'zoos' that we are talking about.
Just my thought.