When betas, also known as Siamese fighting fish, show their breeding or fighting form, they have the appearance of animated Asian watercolors. Bettas are intensely colored – flaming red, cobalt blue, black or emerald green depending on the variety – with veil-like fins spread like wings. They will toss their heads and flare their fins and gillcovers eager to do battle or to breed. In the case of the former, two male bettas occasionally fight until death.
To learn more, read Choosing a Betta Splendens