Banana plants are fine in your aquarium.They don't die if submerged. I have a few in mine, been around a few months now. No problems. Intriguing looking plant. When looked after it grows green vibrant leaves.
You propagate by cutting the tall stalk with the leaf on it about 4 inches from the leaf. Then just let it float at the top in full light. After a while the cut end will begin to grow roots. You can then insert the stalk roots into the substrate and it will grow more shoots.