Buy Duckweeed localy on Craigslist:
https://newyork.craigslist.org/search/sss?userpostingid=7391919122#search=1~gallery~0~0
or Buy Duckweed on Amazon (paid link):
https://amzn.to/4eeSP10
Beauty of Duckweed Aquarium Gardening
New Aquariums More Fun
Duckweed Wild Samples for your aquariums
Aquatic plants and critters in Central park May 2021
Homemade Fish Food Out of Aquarium Plants
Duckweed in Aquarium
Duckweed Fish Food