Parts of a Betta Fish – Labeled Diagram and Quiz

All 10 parts on the diagram

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Head 3

Mouth Water goes in through the mouth and out past the gills. A male also carries eggs in his mouth to his bubble nest.
Eye A fish's eye is rounder than a mammal's. Fish can detect color.
Gill cover (operculum) A flexible bony plate that protects the gills. A betta flares its gill covers outward to look bigger.

Fins 6

Pectoral fins A pair, one on each side. The paired fins help a fish steer, stop and hover.
Ventral fins A pair of long, narrow fins. They are also called pelvic fins.
Dorsal fin A single fin on the centerline of the back. It helps keep the fish upright.
Anal fin A single fin on the centerline, under the body. With the dorsal fin, it keeps the fish from rolling onto its side.
Caudal fin (tail) The tail fin, the main fin that pushes a fish forward.
Fin rays Soft rays are flexible. They often branch toward the edge of the fin.

Body 1

Scales Overlapping scales cover the skin. A layer of mucus over them helps protect the fish from infection.

How this list was compiled: Every name checked on 2026-09-30 against sources read that day: (1) Florida Fish and Wildlife Conservation Commission, fish anatomy (on its freshwater fishing tips page), https://myfwc.com/fishing/freshwater/fishing-tips/anatomy/; (2) Wikipedia, Fish fin and Siamese fighting fish (text only); (3) University of Florida IFAS Extension, Evolution, Culture, and Care for Betta splendens (FA212), https://edis.ifas.ufl.edu/publication/FA212; (4) OpenStax, Biology 2e, 29.2 Fishes, https://openstax.org/books/biology-2e/pages/29-2-fishes. Each name on the page is used by at least two of them. Hints and detail lines are in our own words. Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; nothing traced or copied. Licence: own work

How it works

A long-finned male betta seen from the side with its fins spread. The numbers run from the mouth back to the tail, and a circle enlarges a piece of the tail fin.

Read the full guide

Head first, then fin by fin

Numbers 1 to 3 are on the head: the mouth, the eye and the gill cover. Numbers 4 and 5 are the paired fins, the pectoral fins on the sides and the long ventral fins underneath. Numbers 6 to 8 are the single fins: dorsal on the back, anal underneath and caudal, the tail. Number 9 is the scales and number 10 the fin rays, in the circle.

Paired fins come in twos, one on each side. A side view shows one pectoral fin; its twin is on the far side.
Ventral fins and pelvic fins are two names for the same pair.

Questions and answers

What are the parts of a betta fish?

On the head: the mouth, the eyes and the gill covers. On the body: scales and the fins. A betta has a dorsal fin on its back, an anal fin underneath, a caudal fin or tail, two pectoral fins and two ventral fins.

What are the fins on a betta called?

The dorsal fin is on the back, the anal fin under the body, and the caudal fin is the tail. The pectoral fins are the small pair on the sides. The ventral or pelvic fins are the long thin pair under the head.

Why does a betta flare its gill covers?

To look bigger. Males and females push their gill covers outward to warn off a rival or in courtship. A male meeting another male spreads his fins as well.

What are fin rays?

The thin rods that support a fin, with skin stretched between them like a folding fan. Soft rays bend and often branch toward the edge of the fin.