In my tank this plant has grown about 21 inches and then 12 inches out of the water apparently if you trim the aquatic leaves just below the surface the plant will stay smaller and aquatic. Aquatic leaves are slender and pointed whereas emerged leaves are more round.
I have this in a 55 growing out the top like in the picture. Mine has sent multiple shoots up and out of the water that flower. Once the flowers die a little plantlet starts to emerge from where the flower was. Once the plantlet started growing a few little roots I cut it from the main plant and replanted it.
I believe this is the same plant being sold at Petco as "Echinodorus peruvianus" or "Peruvian Sword", which from what I can tell, "Echinodorus peruvianus" doesn't even exist. I picked up a couple of these not knowing what they were until I came home and started reading. The ones I bought were sold in the plastic tube. I think that because they were growing without water in the tube, they were growing all their leaves like those in the picture. I'm waiting to see if mine develop the longer, submerged leaves.