One of the athetic things is that since the MH
bulbs have all hteir light originating from a point vs having the light emit from a 2' or 3' lenght the intensity is greater and you get a very nice rippling effect when looking at the tank.
bulbs should be placed so they are 2' apart. If you have a 4' tank you should shoot for 2 MH
is a florecent bulb so the entire bulb lenght emits light. The total amount of light might be simular but the intensity is usually consitered lower since the light is spread out over a larger area.