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Thread: Moving to a grow tent, I have a few questions

  1. #1
    Join Date
    Jul 2014

    Default Moving to a grow tent, I have a few questions

    So far I have built a DWC (lettuce raft) and an ebb and flow setup for tomatoes, my lettuce, black seeded simpson, and my gardener's delight cherry tomatoes have sprouted and are about an inch tall with tiny true leaves starting to form. I have a 400w MH lamp which I dimmed down to 50% and tried out for 2 days. Day one was ok, cuz I came home at lunch and misted the plants. Day 2 I did not mist at lunch, and I came home in the evening to several sad lettuce plants which had been baking and dried out too much even tho they were 22 from the lamp.

    Since then I switched to a single 2' grow fluorescent which runs cool and I keep it about 3" away from plants. They are recovering nicely but I need to do something about the heat from that MH lamp.
    My thermometer says 81-84 most of the time the MH is on, reaching near 90 tho without room fan on. However, from what I understand, 77 is the optimal temp for many veggies, is this right?

    Another problem with the MH is it's super bright! The 11x10' room I have the setup in is lit up like daylight, and this room doubles as my study so it is kinda obnoxious. I understand that plants like tomatoes benefit from having 12 hrs of complete darkness to trigger flowering, and that may be a problem giving them darkness when I have to use the study to... study. So to resolve the light issue I have ordered a 4x4x6.5' grow tent.

    I also traded in my light for a 600w MH with enclosed glass reflector and vent holes
    for 6" ducting. I am planning to set up the light with an inline fan sucking air from inside the tent, thru the lamp and out to the study, which I will keep open to the rest of the apartment. With a fan on low, and no MH light, temps in the room will usually stabilize around 77-78, so I'm hoping I can at least cool down the grow tent even if the room stays a bit warmer than normal.

    So I have a few questions.

    1. My air flow is as follows: Surroundings>grow tent>left side of lamp>right side of lamp>inline fan>surroundings. Fan will be sucking, not blowing (snickers allowed). Will my ducting plan be sufficient to keep my plants around 77-80 F?

    2. How soon can I put seedling under my MH dimmed to 300w, and how far should I hang the light above the canopy?

    3. My next question is specific to the ebb and flow setup. How do you change the reservoir water when you have 4-6 large plants in a tray sitting on top of the reservoir container? I cannot just remove the tray and sit it down cuz it has plumbing running out the bottom. I could build a small stand for the tray out of pvc, I guess, but I am trying to avoid more expenses. I have already spent enough, lol! Plus then I will have to build one to raise the lettuce raft up too.

    So this concludes my novel, thanks so much if you even read this far! I look forward to your helpful comments and opinions.

    Kindest Regards

  2. #2
    Join Date
    May 2006
    Los Angeles, CA


    1. The setup you are describing for the ventilation sounds fine but it is impossible to tell if it will keep the plants at 77-80F. This will depend on a number of factors, mainly the temperature of the area surrounding the tent. Generally speaking, the surrounding area will need to be at least a few degrees or more cooler than the target temp, since the tent will always be warmer than the surroundings, regardless of how big the exhaust fan is.

    2. You can put the seedlings under the MH as early as you want; you can even start them under the MH if you wish. Just remember that the younger the plants are, the higher the light needs to be. What you can't do is start them under a weak light source and them move them under a strong light source without at least weaning them.

    3. I would use a rubber grommet or bulkhead fitting along with a shutoff valve; this will make it very easy to drain the reservoir, assuming it's propped up on something. Let me know if you need me to provide links to specific products.
    David G.
    BGH Forum Moderator

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