How big aquarium plants can get really depends on the species of the plant. There are some species of plants that don't grow very tall, and you should keep such plants in the foreground of your aquarium. On the other hand, there are some species of live aquarium plants, for example, jungle valisnaria, that can grow as tall as 6 feet, so you should keep them in the background of your tank. Besides, here is a list of the best tall-growing aquarium plants that can grow pretty tall.