Advice on metal halide lighting

L

laka

AC Members
Dec 10, 2006
67
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Australia
I am going to set up a 6*2*2 ft planted aquarium tank. I have seen metal halide set ups in my local store and i am very much impressed by the brightness and color? I am aiming for 2 to 2.5 watts/gallon initially. i plan an open top as i want to encourage emergent plant growth.
I wish to know the following:

-what color temp do they operate at. Are there different variations or is the choice limited
-what wattage do the globes come in
-how high off the aquarium do the fixtures need to be suspended
-do they operate via transformers ie 12volts and do they have inbuilt fans
-how often do the light bulbs need replacing
-how many fixtures would i need for my tank?

There seems to be a lot of advice on fluoros but not much on halides.
 
MH lights come in a variety of color temps.
Normal wattages are 70, 150, 175, 250
About 12" seems to be the best height for pendant fixtures.
They use ballasts. And they are not 12 volts. Some have fans.
About every 12-18 months.
A pendant fixture will light a 2'x2' area, so three.

MH lights are not used a lot in planted tanks because they are such a concentrated light source. Your tank is a roughly a 180 gallon aquarium. For good plant growth you only need about 400 watts of lighting. If you were to place 3 150 watt MH lights over the tank you would be at 450 watts. And a little more light makes a huge difference in tanks that size. Also they do generate a lot of heat, the bulbs are expensive and need to be replaced more often than some other forms of aquarium lighting.
 
I use Metals and they work like a charm. They do not seem to get hot as the fixture has built in fans, and I keep my water at an even 78 degrees. I use a long fixture over my tank as opposed to pendants, which aim stright down.
Coralife makes a nice fixture with built in lunars, and you can take out the actinic lights and replace them with power compacts. I have the PC's on first thing in the morning and last thing in the evening, with the metals in between, then the lunars at night. I try to simulate a day's true cycle as best as I can.
 
Thanks very much Rex Grigg and Fresh Newby
I am looking at two options for my 180 gallon tank. One is a 6ft light fixture housing 8*3ft 39W T-5 bulbs. The second is a metal halide light fixture 6 ft long housing 3 HID lights and 2* 4ft T-5 fluoros and 4 round nightlights?
If i go for the latter i will only use 2*150W HID's on either end +2 *T-5's will give me a total wattage of 380W. What do you think? What is a better light temp 6700K or 10000K for photosynthesis?

At the end of the day i think both options are ideal . It comes down to what is more pleasing to the eye.Thanks once again
 
I like a range....mixture...not just 10000k
 
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