Air stones are fine in SW, however, whenever we need an airline, we simply drop a piece of open-ended rigid airline into the area required and that's fine.
I believe what Flower is thinking is regarding gas bubble disease, which is not caused by bubbles in the water, but rather supersaturation of gas within the water itself. Air stones do not really add much gas to the water, as each bubble has its own surface tension (otherwise they wouldn't be bubbles). What an airstone/airline does do is bring water up from the lower part of the tank as well as adds surface turbulance, which promotes gas exchange (CO2 for O2) at the surface of the water, as jay mentioned.