HQI vs. Mogul

[BlueAbyss]

To answer your earlier question, there are people who overdrive their MH bulbs... I've heard of running a 150W DE bulb on a 175W ballast. Many electronic ballasts can 'sense' the bulb it's connected to, and will run the appropriate amount of power ie: a 175W electronic ballast will run a 150W bulb at 150W. I don't think this goes for all electronic ballasts, however, and overdriving your bulbs will reduce their life.

I would definitely go no less than 150W with that depth of tank, if you aren't planning anything beyond LPS and softies that should be enough (though PAR values may be a little low at the sandbed). Remember also that just because there are 25 extra watts at the bulb (from a 150W DE) doesn't necessarily mean that you will get that much more light out of your system, this has more to do with the bulb and ballast combination than anything... a 150W 10K bulb on the appropriate ballast could easily produce more PAR than a 175W 20K bulb on a magnetic ballast, though the same may not be true of that same 20K bulb on an electronic ballast.

I went through the same thing when I started my tank... I was originally going to go with T5s.