I would get a root tab and put it about 1" away from the base of the roots. IME, I use root tabs with these and they take off! You will have to wait for the plant acclimate and hit the root tab with the roots. What kind of substrate are you dealing with?
When this plant takes off, it will grow like a weed. Shoots come off and they make long chains of new plants. I had a tank that started with 4 12" plants. They seemed to just exist for about a month. I actually forgot about it since it was in the back of the tank behing some wood. Then one day I saw a shoot come all the way forward. When I looked at the back, it had shot runners 3 feet across the back of the tank. Looks pretty!
