As someone who keeps both, I fully agree that fresh water is much, much easier than marine environments. There is a much different beauty in freshwater tanks. I really like my goldfish "pond" however. They are living in my basement in a hard plastic childrens wading pool. Every one of my 7 comets has a different personality and actually can recognize me. They ignore my wife and anyone else that comes over to look at them, but they come to the surface when they see me. I love it.
Good luck with your conversion and you're right, that is a permanent solution to aiptasia!