Lots of tropicals can be kept outside in warmer weather and you would be amazed at the growth, color and vibrancy when you bring them back in.
So long as it gets warm enough, those mollies could easily go out in a container garden -- just be sure you have room for ALL of them when it's time to bring them back in! With all that fresh air, live plants (you can throw some anacharis or other cheap, easy plants or you could get fancy with some more pond appropriate plants) and free, live food they'll go forth and multiply.