Whats the difference

[SnowZz]

Between t5 ho 12k vs 10k bulbs?

 

[Kristall-99]

Well it all depends on the brand. Of course the 12k bulb is going to have a little bit blue tint than the 10k bulb. You'll just have to look at the spectrum of each bulb to see which one you like the most. What some do is get a lower kelvin bulb (10k)and get an acintic bulb to give it the blue'er look. Many times the lower the kelvin the better the spectrum but it also gives it a yellow tint look.

 

[pat8you]

those are kelvin ratings on the bulb. It is representative of the color spectrum the bulb has. If you think about the color spectrum the higher numbers are going to have a spectrum that has more blue/purple wavelengths where as lower numbers will have more green/yellow wavelengths.

live aquaria has a real basic "summing things up" type article that may explain it a bit better. Good way to wrap your head around lighting.

Aquarium Lighting: Spectrum and Intensity - Part 1

There is more to it but it gets boring real fast. If you want more in depth information let me know and i can give you some articles that are more technical.