Azolla!

We are having success growing Azolla (Azolla filiculoides) in our pond nursery and have been transferring it to the villa pond.  The fish seem to love it, so it is a race between them to see if the Azolla will increase over time.  Azolla has a variety of uses in farming, so it seems to be a good choice for our aquaponics project. It is native to California.

These websites have a lot of interesting information about the biology, uses and issues of Azolla:
Natural History Museum, London
Theodore Payne Foundation
UC Weed Science