When we bought our home as a foreclosure in Central Florida, the pond was overrun with duckweed. When I was reading up on how to eradicate it without destroying the ecosystem of our pond, I learned how great the stuff is!! I used to fill wheelbarrows full of it and dump it in. These pictures are old, before we had the fence up. The girls loved it, and all the bugs and occasional fish I would scoop up with it! It was great for the soil, but it made their poop green and very runny and pretty gross. We have since been able to get the pond under control. Fortunately, there is a pond behind us on vacant property covered with the stuff!! I still give them a scoop every once in awhile from there as a treat, but as with everything, I believe moderation is key.
Just to let you know, that is not duckweed. It is Salvina, a larger and even more aggressive grower. It is great for removing excess nutrients from a body of water, but I would be cautious feeding it to anything. It is actually a fern and never flowers. If you google some pics of Duckweed (Lemna) and Salvina, you can see the difference.