Re: MH Bulb selection (Which Color Temp is correct?)

Hi everyone,

My 120G F/W plant tank set-up continues. I have found a local supplier
of affordable Metal Halide lighting for my tank (actually, its a
hydroponics store) and I'm amazed at how much cheaper they are than my
local aquarium stores.

They sell what they call a MH 175 Deluxe Lighting Kit which includes the
ballast, bulb and reflector for $220.00 Cdn with a MH 175 Watt Clear
bulb, or $305.00 Cdn with a MH 175 Watt /u/day bulb. The units can be
suspended from the ceiling with a hook and chain as is used to suspend
hanging baskets and the bulb can be mounted vertically or horizontally
(I understand that horizontal mounting lowers both the lumen output and
the life expectancy of the bulb by 25%).

This compares to $500.00 Cdn. for the cheapest units at one of the local
aquarium stores. (It's even cheaper than mail order from the U.S.)

I figure that for a six foot long tank I will need 3 of these fixtures,
suspended approximately 15" - 18" over the tank. Is this correct? 

But which bulb should I select? I did some research through the archives
and find lots of references to the MH 175 Watt /u/day bulb (i.e. Color
Temp: 5200K; CRI: 80). I am ASSUMING (I know that it's a dangerous thing
to do - hence this post) that the MH 175 Watt Clear bulb probably has a
Color Temp. of around 4300K (someone correct me if I'm wrong).

Given that this is for vegetative growth in a F/W tank and not for a
marine tank or for growing roses, which color temp. should I select?
Will the lower Color Temp. (and cheaper by $85.00) bulb suffice for my
needs? What about using two bulbs of the lower color temp. and one of
the higher? 

Thanks for the help.

James Purchase
jpp at inforamp_net