Well , the more the better without creating hurricane conditions in my opinion. Saw a Jamaican grow once up in the hills and there's a constant breeze there, plants love it and it makes for sturdier stalks. My grow is 10x8 about, 6 plants heading for scrog next month. 1 ceiling oscillating fan covering the whole ceiling and the rest, 1 fan chest height standing opposite to the 2 ground fans 48" diam each. Also 2 sets of 6" vents intakes and outakes (4vents total). Like I said the more the better. The plants are in constant movement without being trashed by a wind storm, I treat my ladies nice and gentle. Air flow also makes it uncomfortable for bugs and diseases to set up camp.