Using MH and HPS for entire grow

Discussion in 'First Time Marijuana Growers' started by JSpidey, Jul 18, 2019.

  1. #1 JSpidey, Jul 18, 2019
    Last edited: Jul 18, 2019
    Hey guys, I am getting a plan together and I'm deciding on the lighting setup, I plan on getting some autoflowers and in order to minimize labor I was going to buy a HPS with a digital ballast and then buying a MH conversion bulb to reduce labor, dimmer etc, now I know seedlings are in a sensitive stage and using HPS and MH could overheat or burn the plants, and moving the light farther away would cause the plant to stretch too much, but if I could dim down the MH by using the dimmer, could I in theory bring the light closer without hurting the seedlings and therefore reducing stretching without damage? Any help is greatly appreciated. I'm planning on growing in a 5ft x 5ft x 6.6ft tent with 4 plants in total by the way. Thanks
  2. Lots of people veg with mh without issue. I did for years. Some even veg with hps, it can be done
  3. I had poor results using generic(Chinese) MH conversion bulbs and tracked the problem down to voltage.
    The lights were running at 100 volts when they really needed to be at 120v to get the light balance right.
    I ended up finding a Philips MH that did run at 120v using my MH/HPS iron ballast. and the plants grow much faster.
    You could run a Philips SON-T HPS for both, they produce a lot more blue than the average HPS
    Ceramic Metal Halide lamps are very good with a better light spectrum and more lumens per watt than any other CMH I have seen.
    A 300W light puts out the same or more lumens, depending on the lamp you use than a 400W MH.
    • Informative Informative x 1
  4. Both can be done yes.

    I ran 600w hid full strength from sprout, i began at like 36-40 inches away and moved closer every day or too, had nice tight nodes.

    Ended up not being able to go any closer than about 23 inches for the entire of the grow

    Sent from my iPhone using Grasscity Forum
  5. If you are that concerned about burnage theres always cfls
  6. True, I just wanted to minimize labor, having to bring lights in, take lights out etc, I basically wanted to put in the HPS equipment and only swap the bulb to a MH for seedling/veg and HPS for flowering, I was gonna get a T5 setup but then I'd have to swap an entire hood for the HPS ballast after the first week or two which seems very unnecessary.
  7. I heard keeping the HPS/MH about 16" away from the plants is good enough, is that a little too close?
  8. I understand that, my main concern is the plant in the seedling stage, and having to change around the entire light setup after just 1-2 weeks when I could just use MH conversion throughout seedling/veg stage, and swap the bulb for a HPS once she starts flowering.
  9. I see.. however my main concern is the plant in the seedling stage, I know this is a sensitive time for the plants, and I don't want to waste $100 on 10 autoflowering seeds to lose them all to overheating/burns. But if I can run a decent MH conversion bulb through seedling/veg I wouldn't need to take entire light configurations out of the tent just after a week or two (T5 tubes or CFL's) because they're no longer seedlings and are vegging.
  10. By the way I'll be running intake and outtake inline fans with carbon filters for both, a portable AC unit for temps and a oscillating fan as well as a humidifier for the seedling/veg stage and dehumidifier for flowering stage. I'm trying to gain the most yield possible and since it's autoflowering strains I know they don't grow that big. Their life cycle is about 7-11 weeks which adds to the frustration of lighting equipment. I feel as though having to bring lights in/out for these quick growing plants would be a waste of time. I just need to know if using a MH for the seedling stage isn't that dangerous and would allow me to use only one ballast through the whole grow
  11. ?? You're confusing me. You can totally run both in veg if you want and switch to hps in flower. It wont hurt the plants at all. Or run both the entire grow. It's up too you but either way it won't hurt
  12. Okay so I CAN use Metal Halide on seedlings, how far away should I put the MH light? I'll be getting a 600 watt MH bulb.
  13. I doubt I'll have enough room for both to run together, I'll run MH during seedling/vegging and HPS during flowering it's only a 5ft by 5ft tent.

  14. each plant is different, one might like light at a certain inch, another so forth.

    My first grow i used 600w mh and hps.

    At 16 inches my plants would have died lol. Found them stressing at 22 inches so i hang them at 23-24.

    Ended up with a high quality harvest.

    Started seedlings out at like 40inches(as high as light would go)

    check out my grow thread if you find yourself bored, i went thru similar questions as you.

    The plants benefit greatly from MH is veg and HPS in flower. Using both lights the whole grow at the same time would no doubt be better as more intensity and spectrum will be there.

    Just watch the heat and raise/lower if they are stressed at all.

    1 inch at a time and give it time.

    If they stress the next day raise the lights. If they dont stress, lower it, you’ll find the sweet spot.

    Start high, doubt they would stretch if ur using 600w unless you were like 6feet up, mine didnt at 4.

    And if they would, stretching in the beginning isnt the worse thing, can always throw more soil.

    It wont be too intense probably, as you start high as tent allows.

    Sent from my iPhone using Grasscity Forum
  15. Okay, thank you for your detailed explanation, who knows I might try to implement both lights at once. I'll definitely start around 4 feet away then and adjust accordingly. Thanks
  16. For my seedlings I use 150w CMH lights but have used 70w in the past.
    You can pick them up very cheaply secondhand as ex shop lights, they work fine until the plant is about 12 inches high, but they don't have the light throw for bigger plants. A150w MH puts out more light at 6 inches than a 400w at 12 inches. I use them from the moment they emerge, moving the light away has the effect as using a smaller lamp, but I'm cheap and power is expensive.
    The 400wMH I am currently using is a Philips MASTER HPI-T Plus and it's the best 400w MH lamp I have used.
    However I get better growth from my young plants by using 2 150w GE CMH lamps.
    I hope to get a 315w CMH soon, they put out more light per watt than a 400wMH, and the CMH lamps put out a more balanced light.
  17. I decided to take the more complicated route, buying T5's switching them out for MH when the plant is about 2-3 weeks old or when it starts to show its 3rd set of true leaves form. Then when it preflowers switch to HPS.

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