The results are in

[fkshiu]

Originally Posted by Doug

So why not measure the T-5 par on 4ft. 54w bulbs, instead of the smallest they make?

That's a very valid point. A fair comparison would be to compare 48" 54w T5-HOs with 250W MH. Or 24-36" T5-HOs with 150-175W MH.

Why? The majority of people who use 250MH setups have 4-ft+ tanks. The vast majority of tanks of shorter lengths do not have the depth requiring 250W MH (let's just say more than 20"). Shallower tanks running MH are mostly 150W.

Secondly, nobody who is also considering MH runs just 2 T5-HO bulbs. Teks, Aquactinics etc all use a minimum of four T5-HO bulbs for their units. In fact, someone with a 48" long tank wanting to keep SPS/clams is in the market for for a 6x54w T5-HO system.

This is not even counting the variables of reflectors/bulbs/ballasts that can greatly affect PAR readings.

So in other words it should be a fair fight. For example, testing high-end versus high-end systems that an experienced reefer wanting a crisp white look would consider purchasing for his/her display tank:

An fan-cooled 6x54W T5-HO system using individual Icecap SLR reflectors and a 660 ballast with 4 German aqua-blue and 2 UVL actinic bulbs

versus

2x250w MH on M80 HQI ballasts, SLS lumenmax pendants and SE 14K Aquaconnect bulbs.

(Oh, and the measurements should be taken underwater as well).