I have some of this in my pond and I have to say it does indeed have a magical ability to cover the pond's surface completely if you don't keep hauling it out. The non-native answer to duck weed me thinks.
It looks very pretty. One website says that koi "like to nibble on it". I don't know how many nibbling koi you would need to keep it under control.
It does not thrive nor survive in central Scotland. Very susceptible to water temp.
I didn't realise the impact of this species...sigh
The water boatmen seem to be eating mine that fishy sent me. Maybe it takes a time to establish, it looks lovely at the moment. Just collected around the edges. Absolutely no slimey blanket weed at all.
I regret sending you some Lyn There 'is' apparently a species of North American weevil that feeds on fairy moss (Azolla). You can buy some from the company for just £120. A bargain
When I lived in Hull I used to scoop fairy moss out of the pond by the handful. A couple of hundred miles north it just does not survive. Bonus!