Yes if possible keep the ballast out of the room,... my 400w ballast runs about 100*F while on,... so keeping that heat source out of the room is vital to controlling temps. Tho in all reality the bulb generates most of the heat, every little bit helps.


If your looking at running the rescued bulbs, they won't be the right spectrum. Shop/parking lot/ highbay lighting tends to be much higher kelvin rating (8500-10000k) than growing lights (6500k) The whiter light allows us to SEE more colors and details even tho the light is so diffused. But it's kinda junk for growing.

As for the one bulb with the softer spectrum, it's probably old. All HID lights have a limited life span and begin to change spectrum and loose "Par Watts" over time.

Go to the local Hydro store and buy NEW bulbs that are intended for growing, you'll be surprised how much of a difference there is. (Be prepared to drop $70+ per bulb! I'm running the Hortilux 400w MH,.... $130 for a single bulb! And well worth it! :rastasmoke: )
canniwhatsis Reviewed by canniwhatsis on . 400wat mh Hey guys, just wondering how many plants you can grow with a 400watt metal halide.. These are what my medical grow will be under, I have 5 of them with ballasts, and a 1k.. but its a mh too.. will these work alright for the flowering cycle? should I throw in a red or blue led to pump up the flowering period or will the big Hid do alright? Also, whats the yield like for a low stress trained plant grown under a 400watt mh? I know it depends on the plant and what not but a rough estimate Rating: 5