[Icefire]

Sorry but Cree XR-E R2 (one of the highest leds output) put out less than the double of a K2. It also cost more.

Unless someone has a PAR meter and an array of leds, I don't believe leds can be used at under 1:1 Watts ratio as MH/T5HO.

GE 48" T5HO Daylight put 5000 lumens per tube, let say 8 tube on a 120. 40 000 Lumens over a 120 so about 34.72 lumens per square inch.

A single Cree XR-E is capable of 240 lumens. To be able to light the same tank with 40 000 lumens, you would need 166.66 leds.

167 Leds @ 4.5W each, you have 750Watts of leds over the tank.
With T5 you would be @ 432Watts.

Current R2 price are 12$us per leds on a star, no lens included. Just in leds it's over 2000$, to light a 120 at near twice the current comsumption of T5HO.

Also T5HO bulb cost 20$each, last near 2 years each. that's only 800$, still WAY less than leds in 10 years.

So what's the point of using leds?