Polypodiaceae: aquarium ferns and why you do not plant them

Polypodiaceae are ferns, and in the aquarium that brings a practical consequence that surprises many: they are not substrate plants. They attach to rocks and driftwood by a creeping rhizome that must always stay exposed; burying it rots the plant and kills it within weeks. In exchange they are among the most forgiving plants there are, living in low light without CO2 and multiplying on their own.