When planning your grow tent fan setup, you’ll need to purchase several types of fans:
- Circulation fans to provide air movement within the ten or grow room
- Inline exhaust fans remove air from the tent (and also air cooled light hoods).
In this article we’ll discuss how to set up grow tent fans for proper air circulation. Or you can learn more about inline grow tent fans here.
Both grow tents and grow rooms require both fans for circulation as well as separate fans for proper exhaust. It’s not enough just to circulate air inside.
Without exhaust fans your circulation fans will be blowing around stale, hot, humid air devoid of necessary carbon dioxide. Your crop will never reach its potential in that type of environment. So plan for proper air circulation and exhaust when you plan your grow tent fan setup.
Check out our grow tent fan reviews page to learn more about the best clip-on and floor fan models used in grow tents.
Why is air circulation needed for marijuana plants
Marijuana grows best when exposed to a constant supply of fresh air with lots of carbon dioxide (CO2).
Plants need a constant supply of fresh C02 . For outdoor grows this is provided by the wind. To replicate this indoors, its important to keep a constant stream of air movement to replenish the CO2 around your plants.
Your tent’s exhaust system will provide the intake of new air. You’ll need grow tent fans fans inside the tent for air circulation so this fresh air reaches all parts of your pants. Proper air movement will also prevent problems with plants, such as mold, mildew, and pests.
Plants respond to the wind by increasing the strength of their branches. Lots of air movement encourages strong, healthy branch structure which will be needed to keep top-heavy buds standing up close to the light.
Where to set up grow tent fans
Your marijuana will grow best when you have multiple grow tent or grow room circulation fans.
Above the canopy
You want to position your fans so that they’re covering as much of the canopy as possible. Leaves should rustle gently; avoid blasting air right at them or you may notice signs of wind burn.
Below the canopy
Having an additional fan pointed below your canopy will help keep air from growing stagnant underneath. It will help reduce moisture buildup as well which can lead to problems.
An under canopy fan in your grow tent setup will and can help dry out the top layer of coco between feedings, which reduces the chance of fungus gnats or other insects. It can also help dry out water you spill on the tent floor, the outside, which prevents mildew and mold.
Clip fans work well for under the canopy, as do air circulator fans. Check out the Honeywell small air circulator fan or the Amazon Basics 11″ circulator fan if you’re looking for a powerful fan for your grow tent floor.
How much air circulation do marijuana plants need?
You want the fans to be pointed right at your plants so that they’re constantly rustling. The CO2 around your plants needs to be replenished at least every 5 minutes for optimal growth of marijuana plants. A gentle rustling is best. But based on your setup it can be hard to ensure uniform circulation.
Make sure not to overdo the air movement. Blasting a powerful fan may help the plants furthest away get nice air movement, but the plants right in front of the plant may show signs of wind burn.
Different lights may also impact how much air circulation your marijuana plants need. If you’re running 1000 watt air-cooled lights in a tent, you’ll still have to worry about temps and keeping the light far enough from your plants.
Try the hand test once you’ve completed your grow tent fan setup. If you place your hand under the light and it start to get uncomfortable, that’s exactly how your plants will feel.
Increasing circulation above the canopy can reduce heat to the tops of your plants. But it’s no cure for plants that are too close to hot lights, so always make sure to factor in your plant height when inducing flowering so that the additional growth in the flowering stretch doesn’t raise your plant tips into the burn zone.
What sizes and types of fans work best in grow tents
When choosing the best fan for your grow tent there are several consideration. In a large grow room circulation fans with oscillation can be used to maximize air coverage across a wide area. This isn’t possible in a small grow tent, where clip on fans attached to a pole are a better option.
To learn more about choosing grow tent fans, check out our grow tent fan review page.
Clip on fans
Popular sizes for clip fans used in grow tents are 6 inches and 8 inches. Go with the larger size, and keep in mind that’s a measure of overall grill size and not of the fan blade length.
Clips fans mounted on tent poles can only rotate certain ways, your angles are limited because the material itself will get in the way of the shape of the clip and prevent your from fully rotating it. Having multiple clip fans is a great above-the-canopy circulation solution in a grow tent. Clip fans are very inexpensive. They don’t move a lot of air, but in a small to medium grow tent they do the trick well and are also a great way to save space.
Best small oscillating fan for grow tent use
The Honeywell model would need to go on the floor, but the Secret Jardin Oscillating Monkey Fan has a special hook designed for tent poles.
A small oscillating fan for grow tent use is perfect for tent sizes such as4x4, 5×5, 3×3, and 2×4.
Small Air Circulator Fans
Small air circulator fans are perfect for placing on a grow tent floor. Fans in the 6″ to 12″ size are perfect. Some models oscillate, but for most size grow tents you can just point it across the floor to move adequate air without oscillation.
These fans are a great inexpensive choice for a lot of power. Just make sure that your don’t point fans at high speeds directly into nearby plants to avoid wind damage. You’re better off pointing them below the plants, there’s still enough air movement to keep your leaves rustling gently.
The two circulator fans that have lasted the longest for us over the years are the Honeywell small air circulator fan and the Amazon Basics 11″ circulator fan. The Lasko 10″ desk fan is also one we’ve used that did a good job for under-canopy air circulation.
Large Oscillating fans
Large grow tents need a larger solution. Oscillating fans come in lots of sizes, including 8″, 10″, 12″, 16″, 20″, 24″, and 30″. Most of the larger sizes are available as stand fans. Since they deliver air in multiple directions, oscillating fans a great choice for ensuring lots of air movement around your marijuana plants. If you have the room, go for it.
Large oscillating fans on stands work well in larger tent environments. Multiple fans are needed in bigger grow rooms or tent setups, but the chances are if you’re utilizing a very large grow tent you’re probably not reading this tutorial grow tent fans.
Wall-mounted oscillating fans such as the Lasko 16-inch Wall Mount Fan ($60) are perfect for mounting directly to the walls of your grow area, but aren’t ideal for tent grows.
Tower fans for grow tents
Tower fans for grow tents, such as the Lasko 42″ Tower Fan ($64), can provide circulation both above and below your plants at the same time. Most tower fan models oscillate so the can cover and entire grow tent or grow room area.
Oscillating tower fans for grow tents are a bit pricier than some of the cheaper clip-on and desktop fan options listed above, but if your tower fan can cover twice the area you’ll require less fans which can balance out the cost.
The Holmes 31″ oscillating tower fan ($36) is a good cheap tower fan for grow tents, but may need to be propped up a bit depending on the height of your cannabis plants.
Some tower fans offer too much power for small grow tents. But running on low speed and directing air flow at a tent wall can eliminate the chance of wind damage that can occur when blasting strong airflow directly at plants.
Under the canopy circulation
For underneath the canopy air movement, clip fans can be used there as well. High velocity floor fan models are even better since they come in larger sizes and can move more air. They come in sizes both small and large.
Look for fans with multiple fan speeds so you can fine tune the circulation based on your setup. You could even try to rig up a medium sized desk fan underneath, depending on how much room you have on the edges of your tent.
How many fans does your grow tent need?
Two fans is ideal for midsize tents such as 4×4. You can run a single clip fan atop the canopy, and a medium floor fan below. This provides a gentle rustle to all four plants in a 4×4 grow tent.
With a 5×5 foot tent or larger, adding a second clip fan on the other side atop the canopy ensures better coverage. You can run one floor fan below.
For a very small space such as a tent or closet for mother plants, a single small fan would do the trick nicely. With a 3×3 grow tent or smaller, you can probably get by with a single fan, but having two on slow speeds is better.
Safely installing fans in grow tents
It makes sense to lift floor, desk, or vertical fans off of the floor to avoid risk of contact with water. Use heavy duty power strips with built-in circuit breakers to be safe.
Always make sure your fan cord droops lower than the bottom of your fan before you run it up to exit the opening on the side of your tent. Since water will follow the cord to the lowest point upon contact, and adding a dip in the cord will run the water off before it reaches the fan electronics (which is quite preferable than running it into the running fan unit).
Always use a grounded GFCI outlet to run electricity into your tent, similar to what is used in bathrooms. That way you can avoid getting fried in the wrong way from your marijuana grow.
Placing a floor plan on an overturned plastic plant container can help keep it off of the floor. Position your floor fan so there’s no risk of spilling water into it while watering.
Keep extension cords and power strips off of the floor. It’s best to use twisties or cable ties to attach extension cords to the top of your tent to avoid spilling water on them.
There are lots of considerations when planning for proper air circulation in marijuana grow tents and grow rooms. Grow tent fans should be set up so that your tent doesn’t develop areas of stagnant air or excessive moisture. By following these steps you’ll help create optimum growing conditions for your plants, and you’ll be rewarded with a bountiful harvest of dank, high quality buds with maximum potency.