Is a 13000K LED brighter than a 6500K LED? Does a higher "K" value = higher brightness?

No, that is not necessarily the case. "K" stands for Kelvin and merely tells us something about the light colour. Brightness is given in lumen (lm). Experience shows that light colours in the 6000 to 7000 Kelvin range appear to the eye to be the brightest. The further a light colour deviates from this range the less bright it will appear to the human eye.

Save energy!
Save energy!
Find out how LEDaquaristik lighting contributes noticeably to saving energy.