High humidity issue

Hey I have a question for all of you advanced growers…
So I’m having a high humidity issue while in flower. Without any air circulation I’m sitting at about 65% humidity. I bought fans for inside the grobo but they aren’t working well for this issue. So what I’ve found to work is leaving the grobo door open and having my dyson air purifier blow cool air into the unit and now I’m at 40%. so my question is can I safely leave my grobo door open at all times while the lights are on or is there a chance of getting dust and insects inside? Any insight helps


I would only imagine that you will most definitely have dust blowing around if your house is anything like mine, especially if you have an outside fan facing inwards. I actually just got dustmats to put over top the intake fans in the back of the Grobo to try and eliminate that as much as I could…

Insects will be more likely to get in if it’s not sealed.

On the other hand, a high humidity can mean a risk for moldy bud, as you already know…

I can’t say how for certain it is that your bud will get moldy or not, but I’d say it’s almost a double edged sword at this point.

Only solution I can think of is getting a dehumidifier that’s strong enough to lower the humidity in the room your Grobo is in to be the safest way possible?


Thanks. The air coming into the unit is from a purifier so I should be filtered of dust at least. But when I put the purifier behind the unit to blow thru the fan vents it just doesn’t blow thru enough to lower the humidity.

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Thinking about it some more, you’ll probably have a good amount of light leakage with the door open compared to usual, maybe find a creative way to stop that from happening as well if need be. Dehumidifier is still probably the best bet :slight_smile:

Also, be careful for when you’re in flower and you have a 12/12 cycle, I’d be wary about giving it too much light when its supposed to be sleeping, hopefully your grobo is in an area that can be completely dark during this time


Dehumidifier, air conditioning, inside fans pointed toward water in reservoir, pull unit away from wall more, put unit in basement to control heat fluctuations, remove small panel in back to let out hot air, use fan on top of grobo facing back of unit, use cold water when doing drain and fills, open door everyday for 5 -10 min, ceiling fan etc…
All things you can consider to get the humidity under control.
If these things dont work you may have to void your warranty and get a water chiller.
P.s. You can also run your lights after 6pm and keep them off during day to cut heat.


Thanks. I’ll have to experiment. I’ve had the fans facing upwards towards the lights so I’ll switch direction. You guys are awesome!

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Try running in non peak hours. Also i wouldnt recommend leaving the door open


I agree with people here, it’s generally not a good idea to leave the door open for a number of reasons. It messes up the air flow and circulation. Light no longer reflects and bounces off the shiny white paint on the inside of the door so your plant misses out on some light rays.

To combat humidity I went with floor dehumidifiers by VacPlus.

I have both the 1901 and the smaller 1903 models. The upgraded 1901 is way better and has a much larger tank, greater dehumidifying power, and has smart app controls.


Thanks. I just ordered a refurbished fridgidair one. I have to keep my grobo in my laundry room in the basement so it’s probably the most humid spot in my house. Hopefully this works before mold becomes an issue. Thanks for the replies

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How did the new dehumidifer work for you?

Haha I’m still sitting in the mid 40s which might be as low as I can get it.

That’s a lot better than up in the 50’s or 60’s, I think you should be okay! Good to know!

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Yea as long as I don’t have any mold Ill be happy just cuz this is my 2nd ever grow and my first one I lost about a qt of my buds to mold. So I’ll keep on learning and try figuring out tricks. I put mini fans on the inside but they seem to not help much. But I have it in my basement in my laundry room and that’s about the only place I can have it but it’s also the dampest part of my house