Vents at tent bottom

Lil help on the venting. I got the Mars-hydro 2.3x2.3 tent kit am unsure about how much to open vents on bottom. Do I keep them closed? If so is that hard on the fan? If open do I need to open about 4inches in diameter worth of vent or all of the way?

any help please. Pic shows vents.

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i keep mine open but with a twist! i bout me some PUREBURG 1-PACK Cut-to-Fit Carbon Pad 16 x 48 inches for Air Filters Charcoal Sheet and cut them out to fit on the outside of tent vents , and some Strenco 2 Inch Adhesive Black Hook and Loop Tape to make it stick… links below from amazon


If you have smell concerns you would aim for negative pressure inside your tent…
Look out for the tent walls to bulge inwards, that’s when you have negative pressure.

That is all i have to contribute… Regarding climate control I’m not experienced at all…


I had not considered filtering the intake air. Why do you? I mean I know why I might do that but why did you do it?

My vents on the bottom are mesh, and you’ll be surprised how much fuzz collects on them. I vacuum the screen every month or so. Seems to collect more in summer though, probably the higher airflow season. :man_shrugging:


Mine are mesh too…have to keep an eye on them. Any comments to the open-ness of your vents? Suggestions most welcome. First time Gardner here.

I keep my vents open, for a passive intake. I have my exhaust fan set up for negative tent pressure.

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You have convinced me to be brave and experiment. I’m gonna open em up one at a time. See what it does inside.

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Just remember to close them for dark if you are growing photos the screens don’t stop light

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i too have similar carbon sheets on my vents (all open). I keep mine on the inside. i have enough flow when the fan is on so my tent walls are sucked in (negative pressure), but at night, when the lights are off and the temp drops the fan doesn’t run that often (its on a temp control only, the humidifier/dehimidifiers are on a separate controller).
So, when i would come down in the morning it smelled like quite a lovely weed farm. Putting the carbon filters on STOPPED the smell. i also have made some DIY hoods for the outside of the vents to act as light shields. the room the tent is in is on motion sensors so the room lights are off unless i am puttering around outside the tent, but dont like taking a chance of light leaking through the vent/carbon sheets.
I didnt go the handy velcro route the first time, but actually have it in my amazon basket for my next order. i have them attached with tape which works semi-ok. i think the velcro will be killer.

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I have one vent open on the opposite side as the out take, intake on bottom out take on top.

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So do I need to have the vent fan running always or only when light is on or temp is high? I ask because I have mine always running but when I turn it up to try and lower the temp it doesn’t really affect the temp under the light, only the humidity falls. The fan itself is not warm to the touch nor is the light only the driver is warm. Cant get my temps bellow 77-79. Any suggestions it’s 74 in my house.

@Docnraq , my situation sounds a little different than yours. it is definitely cooler outside my tent so, at night, it is helpful for me to not run the fan to prevent exhausting my warm air.
You mention that when the lights are on you cant get the temp down. i had a similar experience until i moved my temp sensor to plant level. (the top of the tent, above the light, doesnt cool down until lights off). i did have to open both lower vents in my tent to get enough air coming in to get it to drop to the point where my fan now runs maybe 20-30 mins per hour during the day.

Due to it being cooler at night, i dont believe the fan runs at all once it cools. my temps range a little more than i would like, Even with a heater set on temp controller, it drops to 70 at night and gets up to 81 during the day.

i have a temp controller that turns the heater on @ 70 and off at 73 and turns the fan on at 80 and off at 76. My humidity controller turns the humidifier off at 50 and the dehumidifier on at 55.

in hind sight i wish i had gotten the Cloudline fan to have that controller handle the airflow/humidity calcs. Like most of the rest of my gear i have my “starter” gear and maybe some day my “now i think i know what i am doing” gear.

somewhere in there i think i answered your original question, NO, you dont have to have your fans run constantly.

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You did, and helped me get my temps more under control. What kinda controller(s) are you using? Also, humidifier and dehumidifier…must have no matter where you live or situational based on environment? Thank you for answering my questions.

So, good questions. Both where you are and where your grow room is are big considerations. if you have your tent in an area (of your house, gargage, etc) where you can easily condition the space to keep it in your tolerances, it makes keeping the tent in range as easy as keeping the air flowing. this would be optimal. that means you would have good temp control in that room and either a LARGER humidifier and/or dehumidifier (sized for the room).
I am in a different situation. my tent is in my basement. in the summer, it stays pretty consistent temperature wise and my humidity is always “high enough” but sometimes too high. since the high humidity only exists in the tent due to all the plants, i opted for a small dehumidifier.

But, once winter came, and it got COLD outside, my basement is now in the 63-67 deg range almost constantly. along with that, even though i have a “whole house” humidifier as a part of my home heating/AC system, down here in the basement, the humidity is barely 32-35.

This space is too large to economically heat with a space heater or keep the humidity up, so, in the winter months i have a space heater, humidifier, and de-humidifier in the tent itself (the humidifer has only produced one or two quarts of water this winter… pretty dry).

i have a humidity controller (bought on amazon so i can show the link). after monitoring it for a week, the RH is better in the room. i need to get better at monitoring the tank cause it keeps running dry (going through about a gallon a day). i probably could have gotten a tad bigger, but i was sure i woudl be keeping it IN the tent, so i am limited for space (3x4x6 tent). since i only have two plants currently everyone is happy. next grow will be spring and i will be doing 4).

if you are in an area where its warm and dry all year, your requirements will def vary.

Here is the gear i am currently working with

Heater - i think this is an ok choice, my temps dip a little at lights out cause i think it takes a bit for this oil fired heater to warm up. i like the fact that it is “slower” to react so i will continue to play with the on/off setpoints 1500W Oil Filled Radiator Heater, Portable Electric Space Heater with Thermostat, Perfect Radiator Heaters for Home/Office (Black): Kitchen & Dining

Temperature controller - 2 sensors. i use sensor 1 to turn my main exhaust fan on/off based on temp. i use sensor 2 to turn the heater on/off if the temp in the tent falls. i have been happy with this Pymeter Digital Temperature Controller Programmable Thermostat Dual Temperature Outlet Heating and Cooling Thermostat for Brewing Fermentation Greenhouse Aquarium Incubation: Home Improvement

Humidity Controller - i am very happy with this so far. if this company makes a temp contoller, i would buy from them Inkbird Digital Pre-Wired Outlet Dual Stage Humidity Controller IHC-200 for Mushroom Ventilator Fan Crawl Space Curing Meat Grow Room Tent Humidifier Dehumidifier: Industrial & Scientific

Humidifier - i like this but maybe should have bought a tad bigger. its a wick type so less “dust” on your plants, but the big thing is that it has an on/off switch (actual mechanical switch) so you can plug it into the controller and let the controller cycle it on/off vs the wetter/dryer dial on the unit. Honeywell Cool Moisture Humidifier, Black, 7: Home & Kitchen

Last but not least the de-humidifier. poor buying choice. although it seems to do the job (i no longer have RH spiking to 70-90%), the issue is that it has an electronic on/off switch. so you cannot control it from the RH controller. being a total control freak, i have a CONTROLLER, i want to CONTROL.
that said, it has a digital setpoint for the humidity and based on the numbers that i monitor, its doing its job. so, all good. small reservior, but high humidity is not my big issue. Vremi 1 Pint Compact Portable Dehumidifier: Kitchen & Dining

hope this helps


Your a gentleman/woman and a scholar! Thank you. Helpful would be an understatement of what that was. You went outta your way to help me. It is appreciated.

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The growing conditions that you described in your last reply mimic my basement tent grow conditions quite similarly. Pretty insightful information with links too. Thank you.