Live aquarium plants are important in your aquarium as it helps regulate the water quality.
All the bad chemicals that your fish waste produce become valuable Fertilizer for your plants.
All Live plants will in turn release Oxygen back into the water while photosynthesizing.
The Oxygen can then be used again by the fish in your aquarium.
Live plants also generally make your tank look more attractive, and as the plants grow your tank will change and always look fresh and new.
Because plants use the waste produced by fish, your water quality will be better, and your fish will be healthier for it.
Plants also play a vital role as protection for your fry when they are born.
Several fish, including Guppies, tend to eat their own young, and it is important to give the fry a good amount of hiding places for your next generation to survive.
I try to choose hardy plants that grow fast and don't require too much light.
The reason for this is that plants that grow fast will use more of the bad chemicals in the water so your water quality will improve faster.
On top of this your tank will look more "filled in" sooner and this quick growing plant will also guarantee a higher survival rate for your fry.