Originally Posted by Bombalurina
Bettas is plural, betta is singular.
Many Latin nouns ending in 'A' are pluralized 'ae'. Many use the singular form, relying on context for clarification. Many animal names in English use one form for singular as well as plural (deer, sheep).
Many experienced (older?) members of this forum pluralize Betta as Betta.
It should always be capitalized too, I think.