My new vents will be 1.5". One will be near the bow, to replace and existing one and the other will be right beside the tank. While under way, there will be a higher pressure at the bow and lower at the side so there should be a flow through the tank. At anchor, if allowed to swing with the wind, same thing. At a dock, you could use a small fan to encourage the flow but that's probably a waste (not a pun) of time; not sure if 1" is enough even though it is very common but most tanks only have one vent so its 100% better than most. Just don't succomb to the lure of the vent filter, big mistake.
Don't believe everything that you think.