Week 1 Seedling 18/6 - lights out question

[Duceduck]

Hi everyone! I've been asking a lot of questions as of late so thanks in advance to all who have responded with advice and sorry for flooding the section with questions.

I'm on D4 and have started introducing 18/6 as of day 3. I have a 2x2 with most of the equipment i think i'll need (intake/exhaust, CF filter, Humidifier, fans etc..) The seedling is in a 2 gallon fabric with FFHF. When the lights are on, i have both the intake and zipper door partially open with the humidifier on and a fan to circulate. This has helped to maintain a more consistent temp of 77-79 and RH of 55-60 (air space but much warmer and high RH at the soil) after some trial and error. I've noticed that when i have the intake fan and exhaust fan on, the RH drops way too low and the humidifier runs constantly.

The question i have is regarding lights out as the light is my only heat producer so turning on the intake/exhaust fan will surely drop both temp and RH. I closed up the intake flap and zipped the door almost completely just to have some vent. I can't see to the bottom of the tent but i'm sure there's some light leakage since the tent is open a few inches. Although the temp is in the mid-high 60's and RH is still around 60 (humidifier is still on), will the small crack in my zipper cause any disruption to my seedling development?

 

[Arthur]

If I can't maintain temps in the mid to upper 70s, I change to 24 on. Or if I'm in flower, and for some reason (like now... rain outside) and the rH spikes with lights out, I change over to 24 on. Or run my lights out during the warmest part of the day.

Light leaks won't be an issue with autofowers.

With photos, I'd get inside the tent and shut it, mark and fix all leaks.

I am assuming your question is about autos, yes? If so, then the light cycle is also a good tool to help balance the environment.
Photos, that's another story.

 

[Duceduck]

If I can't maintain temps in the mid to upper 70s, I change to 24 on. Or if I'm in flower, and for some reason (like now... rain outside) and the rH spikes with lights out, I change over to 24 on. Or run my lights out during the warmest part of the day.

Light leaks won't be an issue with autofowers.

With photos, I'd get inside the tent and shut it, mark and fix all leaks.

I am assuming your question is about autos, yes? If so, then the light cycle is also a good tool to help balance the environment.
Photos, that's another story.

Yes, this is an auto and since some folks do run lights 24, i suppose it wont do too much harm. Thanks for the suggestion of checking for light leaks inside the tent, didn't think about that.

 

[Mañ'O'Green]

Yes, this is an auto and since some folks do run lights 24, i suppose it wont do too much harm. Thanks for the suggestion of checking for light leaks inside the tent, didn't think about that.

The quality of your crop will be lower if you go 24/0 plants need a night time. At minimum I suggest 20/4 I personally run 18/6 for autos.

I have run tests in the past using 3 clones from the same mother in each of 3 grows running 24/0 = largest yield poorest quality. 20/4 was about the same yield with a little better quality but the 18/6 was by far the best quality with a little less yield. It actually cost a little less to run 18/6 but the difference is not huge because the 18/6 took a week longer to ripen than the 24/0.

I have an oil filled space heater to keep the temperature at least 68°F at night. This can be in the lung room if it won't fit in the tent.

 

[Duceduck]

The quality of your crop will be lower if you go 24/0 plants need a night time. At minimum I suggest 20/4 I personally run 18/6 for autos.

I have run tests in the past using 3 clones from the same mother in each of 3 grows running 24/0 = largest yield poorest quality. 20/4 was about the same yield with a little better quality but the 18/6 was by far the best quality with a little less yield. It actually cost a little less to run 18/6 but the difference is not huge because the 18/6 took a week longer to ripen than the 24/0.

I have an oil filled space heater to keep the temperature at least 68°F at night. This can be in the lung room if it won't fit in the tent.

Thanks for the response and i also plan on 18/6 to give my girl a break. I checked earlier and the temp was 67 but RH shot up to 70's since there was less circulation. Not sure that i want to continue testing out the environment since my girls already in there.

 

[Mañ'O'Green]

Thanks for the response and i also plan on 18/6 to give my girl a break. I checked earlier and the temp was 67 but RH shot up to 70's since there was less circulation. Not sure that i want to continue testing out the environment since my girls already in there.

It is normal for the PH to go up at night. Really the amount of water in the air is about the same it is just that the cooler night time air can only hold less water. That is why it is called "Relative" humidity. It is relative to the air temperature.

 

[Simplicio]

If your humidifier runs constantly, then your exhaust air flow is too great.
An intake fan is usually not needed.
You should be able to keep humidity high with a low exhaust fan speed.
The intake fan might be producing too much air flow.
An intake and exhaust fan running together are effectively in series, and their pressures add together.

 

[SuckerPunch]

I turn my scrubber fan off over night which is only 6 hours because I’m on 18/6. Keeps it warmer- my grow box is in the garage and it stays 66-72 at 40-50% rh.

 

[Cannaficionado]

MOG is right on with this. Theres a lot of evidence that shows running a 24 hour on cycle destroys the microbe biome. This is because when the lights go out plants push sugars out of their roots to help feed microbes. Obviously this can be controlled to an extent with organic nutrients but microbes and the plant are a symbiotic relationship. Definitely should take advantage of that even if you run a 20/4 cycle it will still help maintain the biome in the soil.

As for maintaining a good temperature, just keep your house at 70° during the grow and it should be good enough to keep everything moving along. This is what I do and my set up is in a basement so its actually cooler than upstairs but the tent never drops below 67°F lights off. Occasionally during the winter I run a space heater. Nothing huge or anything, I just keep it by the passive intakes and since I leave my exhaust fan running 24/7 it will pull the warm air into the tent just fine when it kicks on.

 

[Drownomatic]

In my 3x3 the 4" fan is set to a constant 3.

I have a reptile humidifier set to 65%, and level 2 of 3 speeds. It goes through about a gallon/day.

I welcome the cooler night temps, I feel it helps the plants show colors, and get a good fade as they mature.