Hygroryza aristata aka Floating Bamboo is the only grass species that is used in aquariums. This is a great plant for open topped aquariums and its roots will provide refuge and shelter for juvenile fish and shrimp if used in a breeding tank.
Floating Bamboo a highly recommended floating plant because it is easy to maintain and will not spread everywhere like duckweed and azolla. Propagation is by trimming off a piece, which will start to grow very soon.