The aquatic ferns can be particular, but are easy to care for when they get what they need. They like warm temperatures, bright but indirect light, and a dilute nutrient solution.
The Salvinia and Azolla are floating ferns that can be kept without a substrate – simply top up dishes with <50 ppm N nutrient solution regularly. Occasionally weed or prune the tanks by removing other species that have crept in and cutting out dead growth and algae.
The Marsilea and Ceratopteris are rooted ferns. They need a fine substrate to anchor in such as 2 cm of growing media covered with 1 cm of Oil Dri or aquarium substrate such as Fluval. The Marsilea can quickly overgrow the dish and needs to be repotted occasionally. It is tough and can be pulled out of the tank, washed of the substrate, consolidated or pruned, and replanted.
The Marsilea roots in substrate underwater and has two growth forms – a “carpeting” single-leaf form and a tall “clover” form. Clovering is initiated in low light conditions and when they are grown in shallow water. The Marsilea increases pH. Check regularly and change water or add citric acid as needed.
The aquatic ferns include the following species:
| • Marsilea hirsuta | • Salvinia sp. |
| • Azolla sp. | • Ceratopteris |