roots need air?
So I just bought and have been reading the big hydro book from this site and I'm confused. In the big bubbler pot set up it says that once there are roots coming down from the pot, then lower the water level so they don't rot because they need air. So how do the roots get the solution if they are not touching it? And why would they rot sitting in the water if the lettuce raft ones are in the water all the time?