Help with duckweed

I'm trying to establish some duckweed in my pond, but it isn't going well. Several times now, I have introduced a smallish quantity of duckweed to the pond, but every time it has been gone by the next day. Thinking that perhaps it was eaten by something living in the pond, I also placed some in a what are basically some deep puddles in some trenches elsewhere on the property. It survived there for about a week, and then also was gone. Finally, I placed some in two different tubs that I left out in the sun, one filled with pond water, one with drinking water. By the next day, in both of these, the duckweed was still floating the next day but was completely pale. I'm assuming it is more or less dead at this point, but I'm not totally sure.

What am I doing wrong? Anything else I can try?

I don't know much about duckweed though I am wondering if you had the plants in full sun?  If so maybe a more shady location might help.

Hi Edward,
Perhaps you could get one of those game cameras to get an idea of what is eating the duckweed. This might help come up with a plan based on what that animal is.

I wonder what would happen if you added a large amount of duckweed?

I'm learning about duckweed this year too.

The frustrating thing is how many people say it's easy to grow.  

So far, I've found my goldfish love eating it so I have to grow it in a separate container then add to the goldfish pond.  If the weather is warm enough, the plants can outgrow the goldfish, but if the temperature dips down, then the goldfish win.  

So far, mine is growing best in dappled shade with warm water (black feed buckets, wider than they are tall).  They go white in full shade and aren't growing so fast in buckets that aren't black.  I keep meaning to look up the ideal temperature for this plant to see if it has a narrow range.

I'm curious to see how it goes for you as I'm still not happy with my duckweed growth.  Cheering you on.  

Healthy duckweed should have long roots trailing below it in the water. One sign of things eating it from below - and possibly killing it if they eat too much - is that the roots are minimal or gone? Small things will eat the roots. Bigger things like visiting ducks, will eat the whole thing - in one gulp and ask for more!

Mine does seem to go pale if the sun is too strong. I would agree with r ranson that it seems to like less than "full sun", but more than "deep shade". I think my bigger pond isn't exactly "dappled" shade, but more that get's shade crossing it depending on the time of day and time of year. My smaller pond has a bit of a line where the deeper shade has none growing, and the more dappled part does.

We use duckweed only to produce human food (Chicken, Pigs and Ducks)

Yes, Wolffia arrizha is an absolute superfood
Lemna minor stands only little behind

BUT,
we started successfully growing, after we over-fertilized our Duckweed ponds, 30cm (1 foot) maximum depth 3x6 meters (9x18 feet) and throw regulary (as soon the Duckweed growth slows down) a 3-4 buckets fresh cow manure into them...

Well who wants to eat that?  

When you harvest it leave about 30% of the plants in the pond..