Lighting for a 120g tank

Hi KB,
> I'm doing preparation for the 2ft deep
> 120gal tank I'll be getting in the next few months. I was reading
> the august issue of Fishkeeping Answer (a British mag) and they
> mentioned that only MH or MV lamps are recommended for 2ft or deeper
> tanks. Flo tubes are for depth of 18" or less. Is this true or could
> I get away with only flo bulbs?

Well, we discussed how light is refracted/reflected inside a tank
which means the inverse square law does not apply once the light
has made it inside the tank. You could use FL lighting to get your
desired ~240w which would imply at least 6 tubes. On the other hand,
this is quite a heavy lighting fixture which would need to sit quite
close to the surface of the water. I think you could very successfully
use a 250w MH pendant which you suspend 12-18" over the surface of
the water. I have one of these over my 49g tank which is 4' in length.
I find the light dispurses very well to the ends of the tank using
a deep parabolic shaped reflector. The bulb needs to fit entirely
inside the reflector or you get a very uncomfortable glare. Initially
I thought I would want two pendants but the more than double costs
for this arrangement dissuaded me. The 250w lights a tank with a
width of 4' with no problem at all. The lower wattage MH systems are 
less efficient and cost more since they are not commonly used. The 
250w+ bulbs are used very commonly. I get my ballast and equipment 
as recycled hydroponics stuff.  The only catch is locating a deep 
parabolic reflector. Here in Canada and the US there is quite a
cottage industry for growing marijuana indoors which allows us
aquarists to take advantage of cheap second hand fixtures etc.
Due to the abundance of tropical sunshine, I don't know if you'll
find much hydroponics there in Penang. If you can find a reasonable
price for it, I'd recommend MH lighting. I got my fixtures and
ballasts including a new bulb for $125 Cdn. One of the real nice
features is that you don't have to mess with the heavy fixtures when
you need to get into the tank. Also the MH system is quite reliable
unlike my old FL setup which I had to keep wiggling the bulbs to
ensure a good contact after many years of high humidity service.

Your fixture should look something like this: 

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                     /       ||  ||       \
                   /         ||  ||         \
                  /           |  |           \
                 /            |  |            \
                 /            |  |            \
                /             |  |             \
               /             /    \             \
               /            /      \            \
              /            |        |            \
              /            |  WWWW  |            \
              /            |   WW   |            \
              /             \      /             \
              /              \    /              \
              /               |  |               \
              /               |  |               \
              /               |  |               \
              /               \__/               \
              /                                  \
              /                                  \
             //                                  \\
Good luck,