i checked the PAR on a few different fixtures and different lamps for my own private study, and found that my 8 lamp t5 fixture put out more PAR than 250 watt halides at the same distance. as a matter of fact, the PAR difference on the sand bed was over 100 more with the T5s.
i used a hydrofarm t5 ho
fixture(for plants), which had a mixture of ATI and Giesemann lamps, and used a reef optix 3 reflector, 14k phoenix bulb, and sunlight supply galaxy ballast for the halide setup.
to the naked eye, the tank looked more blue under the t5 fixture as well.
over my 195, which was 25" deep, i used 250 watters on the outer edges, and a 400 watter in the center. there was a drastic growth and coloration difference towards the center of the tank, under the 400.
yes, the guy had a standard 220, which was 72 x 24 x 30 tall. he kept whatever he wanted wherever he wanted. clams did well on the sand bed. i'm sure his growth would have been better with an extra 2 lamps, but he was happy with the fixture.