pros/cons of MH ballast

in a setup where you have two MH lights, what are the pros/cons of using a dual ballast versus two independant ballasts?

 

I use independent ballasts. Easier to control (such as using my apex - can turn each on individually) plus if one fails you can still use the other - with a dual ballast, if it fails, you're SOL.

 

sounds right to me, I'm thinking the seperate ballasts are easier to keep cool as well as long as they are not stacked on top of each other.

 

Dual ballast
Pro
- Smaller in size in general
- Usually cheaper than 2 separate ballasts
- Less wires
- Need one timer to control both
Cons
- Cannot control each bulb individually (although some dual ballast came with two separate cords or switches)
- Need to replace the entire ballast when busted where only one faulty ballast can be replaced for single

This is all I can think of for now.

 

Alright, pretty much the same logical pros/cons i thought of. I figured I might be missing something else. Im new to metal halide lighting.

Ill go with the individual units because I see they actually can produce better results than a dual as well.

Probably Lumatek or Sunlight Supply havent decided yet.

Do I need the ability to "DIM"? I see there are dimmable ballasts but it seems they just have a selector on the side for 150/175/250 on the dimmable. so basically they're trying to reduce the life of the bulb? as i understand it if you run a MH bulb at lesser wattage than its designed for it'll have a shorter life span.

 

It's your personal preference. I use MH with PC supplement (soon to be T5 supplement) so if it is too bright (when I add new coral or fish), I just turn MH off for light acclimation. Dimmable would be nice but not at the top of my "need" list.

 

You don't need to dim. I would run your bulb at 250, 150, whatever it is rated for. I have 3x250 MH, 2x54 T5, and a 48" ReefBrite LED (equivalent of 2 ATI Blue+ T5's for output). I will have the T5's turn on, then have the LED's turn on, then have the MH kick on one by one: 10, 15 minutes apart and then do the same at night. Slow, gradual "sunrise, sunset." If I were you I would do something similar.