Take care selecting Hornwort though you want one that will stand your pH.
Ceratophyllum demersum (Common Hornwort) and not C. submersum (Tropical Hornwort), over thirty other species listed, probably variants of the two main species.
Grows best for me as a floating plant in not too highly filtered tanks.
(High water movement causes it to move about too much on the surface and thus die.)
Trying to root it is hopeless for me, it just brakes off then the burred bit rots. Rap around decor for the best results (securing it on to decor only lasts a while as it always seems to brake at the point its tied).
Many are cultured at low pHs if so take the pH up slowly or it may die back causing an algae problem.
Very rare for it to be imported from Lake Tanganyika I hear.
But you guessed it. Mine is.