I put some duckweed into the 55G tank in my office about 3 weeks ago.  As of late, the tank is nearly overrun by it.  Therei s a thick mat of the stuff covering about 60% of the surface of the water.  I was looking in and saw a swordtail fry.  I looked closer and saw dozens of them hanging out in the duckweed.  Apparently floating plants really are good for raising fry.  Up to now, I had been moving my fry into a breeder net.  I decided to leave them in the duckweed to see how they do.
I am going to try to get pictures tomorrow. 
The downside to this is more fish in an overcrowded tank.  I need to make friends who have empty aquariums who need fish.