This tiny fern is sold under various trade names, e.g. e.g. "mini Bolbitis", "Davallia spec." and "Bolbitis Davallia spec.". It has nothing to do with the ferns of the genus Davallia but is a dwarf form of the widely spread and extremely variable tropical Asian fern Bolbitis heteroclita. It was originally described as a species of its own (Edanyoa difformis), originates from the Philippine island Negros and has been in horticultural cultivation for a long time. It has only recently been discovered as aquarium plant, though.

Diverse small ferns of the Hymenophyllaceae family are sold under the name "mini Bolbitis", though, and it cannot be said exactly which species they belong to and whether they are suitable for aquarium cultivation. 
 
Synonyms
Edanyoa difformis Copeland, Bolbitis sp. ''Baby leaf''
Misapplied names
Davallia spec.
Trader names
Bolbitis difformis, Bolbitis Davallia spec.
Complete botanical name
Bolbítis heteroclíta (C. Presl) Ching
Family
Dryopteridaceae
Genus
Bolbitis
Difficulty
medium
Usage
Epiphyte (growing on hardscape), Midground, Nano tanks, Foreground, group
Growth
very slow
pH value
5 - 7
Temperature tolerance
18 - 28°C
Carbonate hardness
0 - 14°dKH
General hardness
0 - 30°dGH
Propagation
Proliferating leaves, Rhizomteilung, Splitting, cutting off daughter plants
Can grow emersed?
yes