Lighting: 18000 vs 40 watts??

[zelfin]

What exactly is the difference between the numbers?
I put in some new bulbs on my 75g. According to everything I read here the simple 80 watts of lighting is nowhere near enough. Yet the packaging on both says 18000 and that it is great for all types of marine use.
What is the meaning of those numbers and which should I go by??

 

[bang guy]

Does it say 18,000K or Kelvin? If so that's the color of light the bulb produces. It has nothing to do with power (watts).

 

[zelfin]

It says 18,000k, ok so that makes sense. Then the wattage would just be whats required tog et enough light to filter through the water and actually sustain the tank?

 

[bang guy]

Yep.
80 watts is woefully inadequate for a reef tank and I'd even suggest more light for just fish.