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RE: Lighting

I should have said 175w. My mistake. Since I want to be at the 2 watt a 
gallon level. How high above the tank should these MH Pendants be mounted?


Are you *sure* that 200w light you were looking at is really a metal halide 
(MH) light? I have seen lots (and lots!) of books that incorrectly talk 
about halogen lights (which are basically improved incandescent lights) as 
MH lights. MH lights are *arc lights* that have *no filament*. If the bulb 
has a filament than it is *not* an MH light (or any other high intensity 
discharge (HID) light either).

Typical MH lights come in these sizes:

Normal mogul-base in 175w, 250w, 400w, 1000w, 1500w
HQI (contacts on the ends of the bulb) in 150w and I think also 250w

HQI is somewhat similar to the large halogens that have the electrical 
contacts on the ends, but the HQI will have a little "bubble" in the middle 
of the tube and there will be *no filament* in it. The halogen bulbs will 
be straight tube in most cases and will have a filament running the length 
of the bulb.

I've seen some little 35 and 70 watt MH lights too but they aren't very 

You do *NOT* want to use halogen lights in most cases. They put out way too 
much heat for the amount of light they generate since they are not very 
efficient, and their color temperature is typically lower than most would 
like on their tanks. For MH lights on a 90 gallon tank I think you'll find 
two 175w fixtures to be your best bet. It is common practice to use one MH 
fixture per 2 foot square area of tank surface to help keep the light 
levels in the tank even.


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