Mine is in a 4ft tank with 4 daylight fluorescents (well in need of new tubes). No ferts added or special substrate mix either. If it has the room to grow out of the water I think it will flower. Mine has reached the size the last one was when it did so, so I am keeping an eye on it this time.
My tank has a glass lid and the fluoros are in a reflector which sits on the glass. The whole lot is covered by a wooden lid as it is part of a built in unit so I will not notice the flower unless I look under both lids. :roll: