If you don't wanna pay alot, I've been running a 4" ipower plastic fan(quieter than metal) with filter in a 3x3 with 5 mothers in it. Tent is packed to the gills. No smell.
I checked for reviews before I bought, ipower filters were rated near the top though the price is near the bottom. I've been running it 24 hours a day for 1- 1/2 years. https://www.amazon.com/dp/B07Q53ZH5Y/ref=cm_sw_r_cp_apa_glt_fabc_MZXKCRR0GTWWPBXYF7Q6?psc=1
It's literally the smallest tent I could find that would fit in my closet. I pieced everything off of Amazon to get me started. I'll include links for everything if you'd like.
iPower GLFANXEXPSET4D25CHUMD 4... https://www.amazon.com/dp/B07Q53ZH5Y?ref=ppx_pop_mob_ap_share
https://www.amazon.com/dp/B074J876KK?ref=ppx_pop_mob_ap_share
https://www.amazon.com/dp/B081Q4X3Q9?ref=ppx_pop_mob_ap_share