Crowntail Betta
The largest betta fish species in the world is the crowntail betta, with adult individuals reaching a maximum length of approximately 15 centimeters (about 5.9 inches). According to search results, the common body length of Siamese fighting fish (Betta splendens) is 5–6 centimeters, but as a specially bred variety, crowntail bettas can grow significantly larger. This betta gets its name from the elaborate, lion's mane–like appearance formed by the extension of bony rays in its tail fin. Due to its strong aggressive nature, it must be kept alone to avoid conflicts with other fish.