Fairy Moss (Azolla) has a tiny structure resembling a fern with tiny roots hanging below. It floats on top of the water, so skimmers may need a screen to keep the plants out. It grows about 1/2" across, and is bright green while in the shade. It turns to deep red in full sun. Many fish will eat Fairy Moss.
Fairy Moss is great in finishing filters for removing nitrates that remain at the end of the biological cycle. Fairy Moss helps provide coverage and shade to help starve out algae. To clear green ponds, let the Fairy Moss multiply until it covers your pond completely, then net it out and your water should be clear. It will have sopped up all of the nutrients and blocked the sun which will kill off the algae. These easily netted plants make great compost. 

This sale is for a 6 ounce Dry Scoop (moistened before packaging) in a sealed poly bag which will densely cover about a two square foot area. Fairy Moss can double in volume in days under ideal conditions. You can keep a lasting culture of Fairy Moss or Duckweed in a shallow container in full sun, and feed your fish from it as the plant multiplies. Change water weekly with pond water to feed it and you will have a season long supply. Greens are a very healthy food for pond fish and can be fed even after your water temperature is too low to be feeding man made foods. Can be propagated in aquariums with sufficient light. 
THIS PLANT GROWS VERY FAST IN FULL SUN !.