I just snared some yesterday from one of our local ponds and set it up in my little turtle kids' pool. I put in the old water from the chickens when I clean out their waterer every morning. Apparently, the duckweed loves nitrogen and ammonia and the fouled water certainly has lots of that. Yesterday, it started with enough duckweed to cover less than a quarter of the pool and now it covers more than 3/4 of it. It grows like crazy!
By tomorrow morning, I'll have enough to harvest some and see if the chickens like it. I hope so- this looks promising. I'll try to get some pics later.
And I'd love to hear from anyone else doing this.