Metal Halide

[Wizzard~Of~Ozz]

I recently found out I have access to as many 250w metal halide fixtures that I need. few questions..

Do [acronym:f640ffecc8="Metal halide light"]MH[/acronym:f640ffecc8] bulbs have an effective lifespan?

I would have to make a custom canopy to house them, I assume putting a couple 80mm fans in would be enough to draw out the heat? (2 in, 2 out)

What would be the recommended height off a tank for a 250w bulb? (I would have to center it and use a deflector to get it to the outer part of the tank)

a 250w would bring my 75 [acronym:f640ffecc8="Gallon"]gal[/acronym:f640ffecc8] tank to about 4wpg which I think would be a bit too excessive, can I put a 175w bulb with a 250w ballast? or will it fry the bulb?

I assume a bluish tinted bulb would be a 10k?, how is this for plants?

Should I seal the canopy (cat proof, not air tight) and not put any glass on top of the tank?

Any help would be appreciated.

[travis simonson]

I've always wanted to try [acronym:b891845663="Metal halide light"]MH[/acronym:b891845663] lighting myself but I'm not the best one to answer your questions (and they are excellent questions). I'll bet the reefers in the [acronym:b891845663="Saltwater"]SW[/acronym:b891845663] forum would be able to answer your questions.

[ccCapt]

[acronym:5fceb6ea8e="Metal halide light"]MH[/acronym:5fceb6ea8e]'s on a fw tank may be overkill, but any live plants would probably like it.

Do [acronym:5fceb6ea8e="Metal halide light"]MH[/acronym:5fceb6ea8e] bulbs have an effective lifespan?

On average, you get a year of use before they start to lose the proper color spectrum.

I assume putting a couple 80mm fans in would be enough to draw out the heat? (2 in, 2 out)

That would work fine.

a 250w would bring my 75 [acronym:5fceb6ea8e="Gallon"]gal[/acronym:5fceb6ea8e] tank to about 4wpg which I think would be a bit too excessive, can I put a 175w bulb with a 250w ballast?

[acronym:5fceb6ea8e="Watts Per Gallon"]wpg[/acronym:5fceb6ea8e] doesn't really work with mh's. You will not get anywhere near the intensity of a mh compared to [acronym:5fceb6ea8e="Power compact fluorescent"]pc[/acronym:5fceb6ea8e] or no flourescent which is why mh's are referred to as [acronym:5fceb6ea8e="High intensity discharge lighting (Mercury Vapor and Metal Halide)"]HID[/acronym:5fceb6ea8e] (high intensity discharge). You can not use a 175 bulb with a 250 ballast. Bulb and ballast must be same wattage.

I assume a bluish tinted bulb would be a 10k?, how is this for plants?

10k is more white. You want a blueish tint then go with 20k.

Should I seal the canopy (cat proof, not air tight) and not put any glass on top of the tank?

No glass is needed if you use a light canopy.

[travis simonson]

Thanks cccapt, great advice [acronym:84ca3fda5c="Metal halide light"]MH[/acronym:84ca3fda5c] lighting is a relatively rare thing for [acronym:84ca3fda5c="Freshwater"]FW[/acronym:84ca3fda5c] planted tanks and there aren't many of us who've tried it (yet ). After reading your excellent advice I think I can add a couple of things:

1] I wouldn't go above the 10000K spectrum for lighting plants because, in addition to blue spectrum, they require high green and red spectrum light for best photosynthesis. Staying within the 5000-10000K range will give you good green and red spectrum in addition to adequate blue and prodcue the best results for growing plants.

2] I'm assuming a light canopy would include tempered/[acronym:84ca3fda5c="Ultra Violet"]UV[/acronym:84ca3fda5c] resistant glass. I know little about [acronym:84ca3fda5c="Saltwater"]SW[/acronym:84ca3fda5c] flora and fauna, but a [acronym:84ca3fda5c="Freshwater"]FW[/acronym:84ca3fda5c] tank will require [acronym:84ca3fda5c="Ultra Violet"]UV[/acronym:84ca3fda5c] shielding if lit with [acronym:84ca3fda5c="Metal halide light"]MH[/acronym:84ca3fda5c] or the [acronym:84ca3fda5c="Ultra Violet"]UV[/acronym:84ca3fda5c] from the lights will toast your critters and plants in short order. I know most [acronym:84ca3fda5c="Metal halide light"]MH[/acronym:84ca3fda5c] lights already come with [acronym:84ca3fda5c="Ultra Violet"]UV[/acronym:84ca3fda5c] blocking glass covers so it probably isn't anything to worry about, just thought I'd throw it in in case it matters

[malkore]

Yeah, [acronym:ebe607a682="Freshwater"]FW[/acronym:ebe607a682] [acronym:ebe607a682="Metal halide light"]MH[/acronym:ebe607a682] setups need a [acronym:ebe607a682="Ultra Violet"]UV[/acronym:ebe607a682] shield to be safe for fish.

You typically only see [acronym:ebe607a682="Metal halide light"]MH[/acronym:ebe607a682] used in larger tanks, that are often 24" deep because [acronym:ebe607a682="Metal halide light"]MH[/acronym:ebe607a682] will penetrate that far.

Indeed they have less lumens output for the wattage as compared to [acronym:ebe607a682="Power compact fluorescent"]PC[/acronym:ebe607a682] or [acronym:ebe607a682="Very high output fluorescent"]VHO[/acronym:ebe607a682]. I can't quite recall if they are above or below [acronym:ebe607a682="Normal Output Fluorescents"]NO[/acronym:ebe607a682] fluorescents for lumens output, but I know it wasn't significantly less/more, and the shear volume that [acronym:ebe607a682="Metal halide light"]MH[/acronym:ebe607a682] puts out makes up for its short-comings.

[ccCapt]

Even tho I don't have that much experience with live fw plants, I do agree 10k may be the highest kelvin rating you want to use. If you notice most "grow lights" are about 3500k (I think....lol).
As far as [acronym:18a1bf5ccf="Ultra Violet"]uv[/acronym:18a1bf5ccf] protection, mogul base (single ended) mh bulbs are enclosed in a [acronym:18a1bf5ccf="Ultra Violet"]uv[/acronym:18a1bf5ccf] shielded glass, but dbl ended bulbs would require [acronym:18a1bf5ccf="Ultra Violet"]uv[/acronym:18a1bf5ccf] protection.

[travis simonson]

While less efficient in lumens per watt, [acronym:08ae986b75="Metal halide light"]MH[/acronym:08ae986b75] lighting is typically much more efficient at producing photosynthetically active radiation (PAR) per watt than fluorescents. The PAR efficiency rating is a much better indicator of a light's ability to grow plants (and algae :P ) than its lumen output and efficiency. For more detailed reading check out A Comparison Between Light Sources Used in Planted Aquaria. It is one of the most in-depth explanations of how lighting works in aquariums that I have ever read and explains a lot about why certain types of lighting work the way they do.

[Wizzard~Of~Ozz]

The lumen output of a 250w metal halide is about 19,000 , a typical [acronym:6480e47d2d="Normal Output Fluorescents"]NO[/acronym:6480e47d2d] is about 2500 per 4' bulb (so 1 metal halide is equal to about 8 [acronym:6480e47d2d="Normal Output Fluorescents"]NO[/acronym:6480e47d2d] 4' bulbs), not sure of compact flourescents output..

Thanks for the information, the local fish store here has a 120Gal 5' tank with 2 HQI metal halides (175w) and it grows some of the most beautiful plants.

Stores also use Metal halide HQI's for their "gardens" that you buy your plants from so I thought it was a little more common then that..

Looks like I might have a project on my hands soon. But it won't be running until I get a 5lb tank and a regulator.. I'll also be running at least 1 [acronym:6480e47d2d="Normal Output Fluorescents"]NO[/acronym:6480e47d2d] actinic 4' just for colour.