I might start doing super small starter portions oO.....
How many people are willing to take a couple of leaves and grow them out themselves...?
Just a note, tanks with a string current will hinder duckweed growth somewhat.
I would recommend people take a separate container, fill with old tank water, plop a snail in, place duckweed in, feed snail every day.... you'll have a lot by the end of a week.
@ madamedesu - Duckweed is tiny, smaller than the smallest grain of rice