Male & Female
1) Males have longer fins compare to female.
Since only fully grown males have long fins, and since young male bettas have
very short fins, this technique may not come handy when trying to sex young
immature bettas. Examine the anal fin of young bettas. If it is starting to look
longer than it did before, and kinda pointy at the end, then it could be a future
male betta.
2) Male’s bodies are less wide, and more elongated.
3) Females have egg spots.
Mature adult males don’t have but young male bettas may have. Egg spot is a
tiny white speck, like a grain of salt, located under the female’s belly, between
her ventrals and her anal fin. The spot is none other than the ovipositor tube,
which the female drops eggs during spawning.
4) Males have more beard.
Beard is a membrane located under the gill covers. When the betta flares, he
opens his covers and displays his membrane. When the gills are closed, the
beard is tucked under,usually will stick out a bit. Females also have a
membrane, It just is not as big and usually will not stick out when the gills are
closed.
6) Males blow bubble nests.
Some females blow bubble nests as well but the bubble is smaller and less sticky
compare to the bubble nest builded by males.