Aquarium Lighting - MH

7 May 2007
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One of the most frequently asked questions when it comes to metal halide lighting is which bulb is compatible with which ballast. Most American made bulbs are going to be probe start bulbs, meaning that they have a starting electrode built into the bulb. Most European made bulbs are going to be pulse start bulbs, meaning that they are designed to operate on a ballast that has an igniter wired in the circuit. Often times probe start bulbs will run on pulse start ballasts, but doing so runs the risk of shortened bulb life and possibly creating a fire hazard.

If you plan on changing bulbs in the future, then you may want to consider purchasing an electronic ballast. An electronic ballast can run any bulb at the rated wattage. These ballasts run coller and consume less energy as compared to standard magnetic ballasts.

Double-ended metal halide bulbs, often referred to as HQI, are available in 3 wattages: 70 watts, 150 watts, and 250 watts. These bulbs require special ballasts to operate.

Iwasaki bulbs are actually mercury vapor bulbs and should be run on an EYE or mercury vapor ballast (250 watt - H37, 400 watt - H33). Iwasaki bulbs are available in 6500K.

The typical lifespan of a metal halide aquarium bulb is about 12 months.

How much time will it take to restart a metal halide bulb after I turn off the power?

After a metal halide bulb is turned off, it could take as long as 10-12 minutes to restart.

Why does my metal halide bulb flicker and turn off?

New metal halide bulbs require up to 100 hours to burn in and could flicker or turn off during that "break in" period. If your bulbs are not new and flicker or turn off then you need to check that you are using the correct ballast for your bulb.

Can I overdrive a metal halide bulb?

With the exception of Radiums, no. Overdriving a metal halide bulb could possibly explode or damage both the ballast and bulb.

Can I run a metal halide bulb on DC current?

No, most metal halide bulbs are meant to be operated on AC current only.

How many hours each day should I run my metal halide?

When operating your metal halide without any supplemental lighting it is suggested that you run them 12 hours per day. When using supplemental lighting, such as VHO's or compact fluorescents, you can run the metal halides 8-10 hours per day in conjunction with 12 hours of supplemental lighting. For instance, the supplemental lighting could turn on 2 hours before the metal halides and turn off 2 hours after the metal halides do.

Do metal halides need a UV shield?

The outer envelope of a single ended metal halide bulb filters out most of the UV rays emitted from the arc tub. Double ended bulbs on the other hand do not have an outer envelope to filter UV, so it is necessary to use tempered glass to filter the UV rays.

How many metal halides do I need for my aquarium?

The general rule of thumb for even light distributution is 1 bulb for every two feet of tank lengthwise.

Do I need to supplement my metal halide lighting with actinics?

Although it has been proven that light in the blue end of the spectrum is beneficial to corals, the decision for actinics usually comes down to aesthetics. Bulbs in the 5500K - 6500K range are considered to be on the yellow side, and should be supplemented with actinics. 10,000K bulbs can stand alone but most aquarists will use actinic supplemental lighting. Any bulb above 10,000K can most likely stand alone without needing the use of actinics.
do 150W 20K DE MH bulbs promote coral growth?or do they need to be supplemented with 150W 10 - 14K bulbs?
they wont stop your corals from growing, but they enhance the colours more and give off a more blue light
dude i cant mention brand or place sorry
Mekaeel IMO a 150w 20K bulb is purely for decoration. PAR is very low on them. If you going to be using energy burning a MH globe then go with something in the 10-14K range and use T5's or T8's to supplement.
dude i like my mix of 14's and 20k's give it that blue crisp look but not to blue
How doesn't look right ? - Not blue enough ?

Remeber what looks nice to the eye is not neccesarily beneficial to coral health / growth.
I would say if anything you could change to 10k out to 14k but in the 150w range I would go higher than that. Anything more and you just wasting electricity.
Guys I`m a little unsure about single ended vs double ended.I`m looking at using 250w lamps ,how do I chose between the two?
I would like to differ from the opinion that MH bulbs need to be replaced every 12 months. To me that is a sales gimmick. Lots of MH bulbs are rated with a 2 to 4 year lifespan. I'm sure MH bulbs can be used up to 18 to 24 months. Maybe some one with a light meter can do some tests in the long run.

My 2c
Cybervic I think the answer is to calculate the number of hours that you burn the light for.On some of my tanks I run the MH five hours but on my tank in the lounge the MH burn ten hours.So I agree the one can`t always say dump the bulbs after 12 months.
6500k for pure growing speed

in between is best of both worlds or a mixture

20000k for blue look

Welcome zookeeper :)

In my opinion I think it is worthwhile going with 250w purely due to the fact that there are many more options available to you with regards to reflectors (spyder, luminarc etc.), whereas with the 150w bulbs you basically have 2 reflectors, the crappy swivel type and a round type.
Viper I have DIY some Lumasomething reflectors now I need to decide on double ended or single ended 250 w
Great thread Copperband.
Please tell more about "the arc tub". How do these lights actually work?

The pure actinic spectrum sits at 55,000k and is acording to Eric Bornemann esential for good coral growth.

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