metal halide 10k or 20k

[kjswift]

what is the difference between 10k and 20k as far as growth, etc.?

[::pete::]

More growth with the 10K, but more color with the 20K and still growth.

[alexwolf]

I much prefer the look of the 20k. I cant stand the way a 10k colors my corals. However, dont try to take pics with all 20k's, they seldom come out.

[captexas]

As far as the looks, it is up to the individual. It is also affected by other supplemented lighting such as VHO's and power compacts. Also, the different brands of bulbs have a different look to them even though they are supposed to be the same rating. Overall, the 20,000k bulbs are a little on the blue side, the 10,000k very white, and the 6500k Iwakis are yellow. You can balance each one out with different supplemental lighting to get the desired look you like. You will get more growth as a response the the lights using the 10k versus the 20k. As far as how it affects the color of your corals is a matter of opinion.

I have a 75g reef tank. Originally I had two 400watt 20k XMs with 220watts of VHO (one 50/50,one daylight). The color overall was nice, but the coral growth rate was super slow. I changed to 10k XMs and all actinic on the VHOs. The tank is much brighter compared to the original setup and the growth has increased. I haven't noticed any change in coloration of my SPS, but did notice it in my zoo's.

[kjswift]

thanks for all the info!