i have (4) 120mm cheapo fans i got in a bulk auction on ebay (still have quite a few left over LOL). they are in my canopy & all wired together in parallel. running them off a single laptop power supply & they barely make any sound.
i'm just gonna put them on the timer that controls my daytime lights & have all 4 running whenever the main lights are on. eventually, i'm gonna get a controller & then the plan is to seperate them on 2 different power supplies & have them come on in stages depending on temps of the bulbs, canopy, &/or water
for the sump, i'm just gonna have a lil $10 6" desktop clip-on fan i have laying around