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Will a 20k bulb be ok to veg


New Member
I'm doing a small closet grow and heat is a big issue. I tried one 400w metal halide and I have to keep the door wide open to keep the air temp about 85

I have a 250w balast and bulb from my saltwater fish tank that I set up. Only prob is the bulb is 20k. I figured if it grew coral it could grow pot.

The 250w keeps the heat down big time


New Member
Re: Will a 20k bulk be ok to veg?

20,000k will be great for veg. due to their color reference index usually 90 or greater. usually 93.
a good hps has a cri of like 70.the 20k is a aquarium bulb but it gives off less lumens. good for veg. cri is the % of actual blue ,red, yellow etc. it recieves. keep it closer to your plants than a reg MH. for better lumens.
a very low level of red, orange and yellow, high amounts of blue. a 14k would be more for growing.
its similar to growing at a higher elevation. i have a 7.2k opti blue ushio mh and leds for veg.
more lumens but a lower cri.


New Member
I used T5 setup from my reef tank with mixed bulbs that simulate 14K. Next grow I switch 5 of the 6 bulbs with 6k bulbs. The 14k cause the plants to be short with wide leaves spread. The 6k bulbs produced a somewhat taller plant with more branches. I know this is not 20k mh, but the higher color temp light should work fine. I will on my next grow use 14k mh from my aquarium since I broke down my reef tank. Great question.

I thank from room temp and electric cost reasons I will use my T5 setup for veg, then switch to my HPS 400w air cooled light setup.
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