not sure, mine was tall and lanky until it filled out, but mine is in a 100 gallon tank, so I don't know if that made any differance.......

hi
Grew several in an outdoor 150 gallon tank it actually grew above waterline of 27 inches and flowered lol.
developed an unfixable leak in the tank so transferred all the water plants to a 15 inch deep water garden.
Don't know the cause but instead of growing up has actually spread out ,leaves being much wider than tall. As usual it has went dormant for the summer . I figured it would croak in the pond lol.
There are several species of this plant as well as hybrids ,good luck telling the difference before purchase lol gary