Azolla - Mosquito Fern
Floating plant resembling duckweed or some moss. Small & has scale-like green leaves. Their leaves will turns pink/red colour when enough strong light is provided. Excellent for filtration and coverage for small fish. Similar like duckweed, this can be used to draw up nutrient in your tank/pond and hence may reduce unwanted algae.
Excellent companion for goldfish as they will leave this plants alone.
This plant can also be used as fertilizer if they are starting to grow more than you need. What you need to do is to scoop them out and spread them on your food garden or trees.
Colour of Azolla will change depending on the season - you may get red or green plants