15 watts should be a good amount of light for a 5 gallon tank. I would expect algae until the water parameters are set to a range where algae growth is less stimulated. It would be at a point where the algae has to compete with the higher plants for food. I think 15 watts in a five gallon tank will work with banana plants.
As for the low maintenance area. The best I can say is limit the lighting. 5 hours can be enough to support a few plants and limit algae. You should get a filter rated to 10-20 gallon tanks to keep the water clear. You'll also need some gravel for the biological filter to help manage the ammonia, nitrites. I'm still figuring out the nitrates. The bacteria that removes it uses oxygen and there's more in the water than the nitrates so they'll use the oxygen in the H2O rather then the oxygen in the NO3.
