Sold as halfmoon when the tail opens to a full 180 degrees at flare, and as super delta when it stops short of that. Suppliers vary, so the same label covers everything from a clean half circle to a wide delta. The finnage is heavy, so gentle flow and smooth decor keep the edges intact. Expect the fish to rest more than a short finned one does.
In the wild
The 180 degree spread was built in Europe by Guy Delaval, a French breeder whose fish reached a full half circle in the 1980s. Rajiv Masillamoni bought two of Delaval's males and crossed the line to an American doubletail male, producing the green male recorded as R39. Masillamoni's fish were shown at the 1991 International Betta Congress convention in Milwaukee, where other breeders took stock home and the halfmoon name was coined. Wild bettas have nothing like it.
Good to know
Tail spread is polygenic rather than one switch, so halfmoon, super delta and plain delta can all turn up in a single spawn. The fan needs more caudal rays and more branching, and the delta family behaves as recessive to the veiltail. Pushed too far, the branching gives rosetail and feathertail, with ruffled edges and a tail heavy enough to tire the fish.
Did you know
Halfmoon keepers trace the form back to one green male recorded as R39 in a breeder's notes. The claim that every modern halfmoon descends from that fish is repeated in most histories of the line.
Common questions
Is a Halfmoon betta a different species from the Betta?
No. A Halfmoon betta is a variety of the Betta, Betta splendens, and it wants the same tank, water and food as the species.
What size tank does a Halfmoon betta need?
A Halfmoon betta needs at least 7 gal (25 L). It spends most of its time in the middle.
How big does a Halfmoon betta get?
An adult Halfmoon betta reaches about 3 in (7.5 cm).
2.4 in (6 cm)11 gal (40 L)72–82°F (22–28°C)
3.9 in (10 cm)20 gal (75 L)72–79°F (22–26°C)
3 in (7.5 cm)20 gal (75 L)72–81°F (22–27°C)