The Water Sprite or Fine leaf Indian fern is a highly decorative, fast growing fern that’s suitable as solitary plant in larger tanks. It is also labeled Ceratopteris siliquosa and C. thalictroides "Fein".

This aquatic fern grows submerged and also as a floating plant. It is recommended to put the leaf rosette of Ceratopteris species not too deeply into the substrate. The "heart" of the plant where new fronds develop should remain above the bottom surface.
However, when water sprite is delivered as potted plant, it often has hardly roots and detaches easily from the rockwool substrate during transport. But the plants will grow new roots in the aquarium. They can be floated until the roots are long enough for planting, or pinned onto the ground with a plant pin (e.g. JBL - ProScape - Plantis) right away. New plantlets may sprout on broken leaves.
Also the planting of young Ceratopteris plants from tissue culture may be somewhat difficult. The plantlets are often entangled and not easy to separate from each other. Also in this case they can be floated until their roots are grown longer. It is also possible to plant or attach clumps of several plants.