Several years ago one of the regulars here found an almost foolproof way to plant those tiny plantlets. He lowered the water level to just barely above the substrate, then planted the little plantlets on the substrate, and let them grow there until they had spread out a lot. Then when he added a full tank of water the little plants stayed there. He called it the "dry start method". I haven't heard of a way to get them started with a full tank of water, but I'm sure someone has found a good way and will tell us about it.
(my dumb look)