Metal Halide Lights

[craigholman]

I have a 90 gallong corner tank. I have metal halide lights that has one burned out light. It says on the light Radium 250W HRIT
I want to replace this but find there are many 259 W metal lights. What is the 10000 K vs. 20000 K. What is the K meaning? Any suggestions as to which way to go. I have soft corals but hope to add acropora frags in the future. I would like a tank I have the ability to place most corals in. Thank you. I knew I should have taken electronics. I have learning each day that I have a lot to learn. Thanks.

[Ne0eN]

Color temperature is a measurement in degrees Kelvin that indicates the hue of a specific type of light source. 10,000K is equivalent to midday sun. Higher temperature gives more blue color, at the expense of PAR value (light intensity)

-- Rob

[raddogz]

If you would like a direct replacement, you will be looking for a SE (single-ended) 250 watt Radium bulb (they only come in 20K).

K refers to thousand, hence 20K.

10K bulbs tend to be whiter or yellower (sp?) - not the bulb itself, but the light that radiates from it. 20K bulbs tend to bluer in color. It reallys is a matter of preference as far as what you want the color of the tank to be.

You will see 12k and/or 14k as well - it fits along the same lines as above one is a little whiter while the other is bluer.

I hope that helps. Any pictures?

[theatrus]

Here is a rough idea how different bulbs look:
http://www.cnidarianreef.com/lamps.cfm

Since you have a Radium bulb, you either have an HQI ballast or an Electronic ballast. Knowing what ballast type you have is essential to figuring out what bulbs will run with it.

If you liked the look of the Radium, I would go get another. They're a very good bulb, but on the pricey side.

[Ne0eN]

Also, Radium is just the brand of the lightbulb (German). You can try finding it on the net, or just buy any SE (single ended) metal halide 250 W bulb. If you do not have actinic suplementation (doesn't sound like you do) I'd replace it with the same 20,000K color temperature. How many inches over the water is the pendant light?

-- Rob

[Ne0eN]

Actually K refers to Kelvin scale. The correct way of representing this value is 10,000K or 10K K

-- Rob

Originally posted by raddogz
If you would like a direct replacement, you will be looking for a SE (single-ended) 250 watt Radium bulb (they only come in 20K).

K refers to thousand, hence 20K.

10K bulbs tend to be whiter or yellower (sp?) - not the bulb itself, but the light that radiates from it. 20K bulbs tend to bluer in color. It reallys is a matter of preference as far as what you want the color of the tank to be.

You will see 12k and/or 14k as well - it fits along the same lines as above one is a little whiter while the other is bluer.

I hope that helps. Any pictures?

[Ne0eN]

Originally posted by theatrus
Here is a rough idea how different bulbs look:
http://www.cnidarianreef.com/lamps.cfm

Since you have a Radium bulb, you either have an HQI ballast or an Electronic ballast. Knowing what ballast type you have is essential to figuring out what bulbs will run with it.

If you liked the look of the Radium, I would go get another. They're a very good bulb, but on the pricey side.

Actually, very good catch... I forgot radium bulbs use HQI ballasts.

-- Rob

[theatrus]

Yes, K here is Kelvin. The "color temperature" rating is the wavelength of light emitted by a true black body radiator when it is at that temperature (in degrees Kelvin). But since lighting sources aren't single spectrum emitters, various manufacturers use various averaging and other methods to come up with the K rating.

But in general,
20000k = blue
15000k = less blue
10000k = "cool" white
6500k = natural yellow daylight
3000k = tungsten light bulb

[craigholman]

thank you all for the help................