Atrial Fib intermittent?

My cardiologist knows I have intermittent A-fib. I can be having a normal day and A-fib will start. Very often I will walk up quarter mile incline to successfully convert it to normal. He has prescribed pharmaceutical grade fish oil. Which, since I have started it. reduces my episodes to once every two months or so. I avoid caffeine which helps. Does anyone know any other "natural" approaches to help reduce the frequency of episodes?