Azolla (sometimes referred to as Fairy Moss) is a floating pond plant that is a fern. It is defined by its finely toothed leaves. Azolla turns red in the spring and again when the temperatures start to cool down. In addition to floating, it will also grow in damp soil or on moist rocks. 

Light Requirements: Full Sun to Shade
Water Depth: Floating
USDA Hardiness Zones: 9-11