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mirth_gw

ebb and flow and grow tent ducting questions

Mirth
9 years ago

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 the grow tent you see here: http://www.amazon.com/gp/product/B00H9O6UJ0/ref=oh_details_o01_s00_i00?ie=UTF8&psc=1

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
-A.H.

Comment (1)

  • grizzman
    9 years ago

    Hello Mirth. It sounds like you've got your hands full with hydroponics at the moment. Though I don't grow under lights I will share what I can / know. I'm sure there are others more experienced who'll help fill in the areas I can't.
    As for changing the rez. Well that is the 1st rule that most of us learn the hard way. Always consider a means to change nutrients during the planning stage. Trust me, we've all been there :-) Probably the easiest fix for you currently is to add a drain into the bottom of the rez container and either elevate the whole system so it will drain or attach an external pump to pull the nutrient out. If you have a hydro store nearby go buy the adapter and then modify the fitting so PVC works. From there you can attach a valve for easy on and off. Personally I use drains on all my reservoirs for the plumbing issue. But in the future you may not want the EnF tray on the rez and be sure the connecting plumbing is flexible.
    As for your venting plan, it will work BUT as you recirculate the air in the study it will increase in temperature as it picks up heat from the lamp so eventually the whole room will hover around 90 degrees. Unless the room has its own window AC unit, your house AC will probably not handle the heat correctly. Also, the increased humidity will make changing the temperature more difficult. You best bet with venting is to have your intake and output vents go somewhere where temperature is either unaffected or of little concern. (i.e. discharge into the attic)
    Onto another topic; If you're growing Marijuana the 12 hour light cycle is necessary (don't forget the one hour on in the middle of that cycle I've been told). Tomatoes (or most of them) are not light cycle dependent to flower and fruit so you don't need that kind of dark cycle. If it were me, I would adjust the lighting cycle so the plants "night" cycle occurred during times I would likely be in there. But yeah, the freaky plant lighting can be kind of unnerving. I have grown indoors before just don't do it regularly.
    As for lighting and plants, I believe the rule is: if you place your hand at the top of the plant and your hand gets hot from the light, the light is too low. If you can vent the light adequately so the tomatoes can near touching the glass you'l have a lot better success growing tomatoes and lettuce together. Otherwise the lamp height is dictated tomato and it get really far away from the lettuce plants.