Metal Halides

I am currently running 2 metal halides with 2 actinics for my 120 gallon tank. My halide bulbs are 175 watt and on the bulb it says 5500k. I just bought 2 new 175 watt metal halides that do not say 5500k on the bulb. I am getting a very yellow colour from these bulbs. What does 5500k refer to and is this a special bulb that needs to be used in the reef tank?

 

well this is a very debated subject anywhere you go..but for sure your 5500k is not what you want!

a general rule is a minumum of 6500k rating.
the rating is really easy to understand, th elower the number, basically the more yellow, or orange the color spectrum, the higher the number, the more crips white and blue colors you get, which is what you want...

i think the most common kelvin raiting is usually 10000k bulbs, usually complimented with actinic blue VHO's or PC's

runner up to that would be 6500k bulbs with the same compliment of the VHO's or PC's

but for certain the 5500k bulbs, all though cheaper, are not as efficent for a reef

 

good answer Uber

Even the 10k's will be yellow for the first couple of weeks until they burn in.

The higher the kelvin, the whiter or bluer they get. Most 10k's are a crisp white. 13k, 14k, and 20k's are adding increasing amounts of blue. However, they have an impact on PAR so you usually have to jump up to 250w or 400w ballasts for the 13, 14, and 20k lights.

You can run 10k fine on just about all 175w ballasts. There is an excellent thread right now on this issue called MH Ballasts.....