When works on this plant, I found out that it is not-as I assumed hatte- is a aquarium, but a terrarium, most marsh plant.
If anyone successfully maintain the long-term Regenschirmfarn underwater -in aquarium, let him tell it here. Otherwise, I adhere to relevant technical articles on the internet and stay with the statement that is not part of this fern under water, but the terrarium / Paludarium!
