5x5x7 Grow tent with 15 cxb3590 6" vs 8" duct fan

Hello all,

Planning to purchase a duct fan and a carbon filter. Can't decide between a 6 and an 8 inch duct fan. Do you guys keep the fan running the whole time? Do you buy one of those temperature controllers and select the range and let your fan maintain a certain temperature? How do you guys run your duct fans? is it a 247 thing? Planning to grow 4x plants.
Please help.

A 6" is more than enough but get a filter rated higher than your fan's rated CFM.

Also get a Temp/RH controller so your fan only comes on when it's told to. A speed controller is also good to have so your fan is much quieter.

Don't buy separate Temp/RH controllers or you'll be dicking around with settings all the time. The combo units are set and forget.

You won't be sorry.

I just purchased the phresh hyper 8" 710cfm extraction fan for the exact same grow area with phresh 200x500 carbon filter rated at 750cfm .i know seems over kill as after you do the maths for that size room its 232cfm .so my thinking is i can have the extraction fan on about say 20-30% keeping the noise down and wear of motor and that % should clean out the room easily.the other fan bringing air in is an 6" hyper 315cfm.
I actually bought the 6" separate same as the 8" extractor but both with speed controllers..as silly me didnt see the combo they had with the smscom hybrid controller 4a mkii minus filter couple pages into the site..i also bought the smscom .with those speed controllers is it as easy as just unplugging them from fan and plugging the smscom into them or is controller fan all in one...

Why are you buying cxb3590s?
Why arent you buying quantum boards?

Fans are 24/7 if smell is a worry.

Get a good filter. The cheapos pale by comparison. They work but my 4 inch CANfilter outperforms my 6 inch cheapo. The difference is amazing.