Betta Anatomy – Everything You Need To Know

Betta Fish Anatomy

I mentioned in one of my first posts that my plan is to feature a new betta fish every couple of months or so, to help you identify them more easily. I’ve already started doing that but I just realized that it might be a good idea to post some information on the betta anatomy to make it easier for you to pinpoint the differences between the different betta fish out there.

Betta Anatomy

To start off, I though it would be handy to show you the following diagram:

Betta Anatomy - Outside view
Betta Anatomy -- Outside View
I’m not going to get into details about the internal stuff too much, since like most fish, bettas have a stomach, liver, brain, anus, etc. I’m more interested in the exterior parts of the betta fish and what makes it tick.


As you can see in the picture above, all bettas have these common fins:

  • Dorsal fin – This fin is located at the top of the betta. This fin keeps the betta stable in the water and allows it to swim straighter. The shape and size of the dorsal fin vary in different types of bettas. Without the dorsal fin, your betta would find it hard to swim in a straight line as the fish follows a certain trajectory when it is swimming. A betta may survive in captivity without the dorsal fin because it is being fed. But in the wild, a damaged dorsal fin can lower the accuracy of the fish when it is hunting, reducing its chances of survival.
  • Caudal fin – Basically, this is the betta’s tail and it is the main piece of the puzzle when trying to identify a betta. This fin is what propulses the betta forward when swimming. The caudal fin comes in different shapes, colors, and sizes. The caudal fin is the reason why betta fish are so popular as it gives them a glamorous appearance depending on which one you get. But a betta fish in the wild doesn’t have flowing elaborate caudal fins as this reduces the speed of the fish, which makes it prone to attacks. Betta fish are selectively bred in captivity for their long flowy caudal fins which make them beautiful. Bettas can have different types of tails. One of the most popular is the veil tail. Others include the delta tail, butterfly, double tail, half-moon, rose tail, plakat, crowntail and many others. The caudal fin is fragile and could be nipped during fights or even on its own when bettas become bored. The webbing of the caudal fin is also vulnerable to a disease known as fin rot. Look out for this as it is an indication of the health status of your betta fish.
  • Pectoral fins – These are small fins located on both sides of the betta, near the gill covers. You’ll see them move around when the betta is idle in the water. The pectoral fins are commonly referred to as the ear of the betta fish. When the fish is moving, the pectoral fins will be in constant motion. The size and color of a betta’s pectoral fins depend on its age and species.
  • Anal fin – The anal fins are located behind the ventral fins and opposite the dorsal fins under the fish. Basically, they are located at the bottom-most part of the betta. Again, it is used for stability.
  • Ventral fins – Also known as the pelvic fins, the Betta fish uses the ventral fins to turn, stop, swim, and descend and ascend in the water. Male Betta have bigger ventral fins while the female has smaller ventral fins. Located at the bottom-forward portion of the betta. They are used for steering.



Gills / Labyrinth Organ

Like all fish, bettas have gills that are located on each side, which let them take in oxygen from the water. They also have a “Labyrinth Organ” which basically lets them breathe air from the surface of the water.


Bettas don’t have eyelids so when they go to sleep, they won’t blink or close their eyes. Apparently they are also near-sighted so they only see things a few feet away, or closer. The eyes of betta fish protrude out of their heads in a bubble. The center of their eyes is usually visible and has a dark color. The outer part of the fish can have different types of color and varies from fish to fish. Bettas have very good eyesight, although they are near-sighted. Their vision is fully colored, and they can see their environment clearly, a testament to their aggressive nature whenever they see an intruder, such as another male. In fact, they even flare up at their own reflections. One thing to keep in mind, when it comes to the eyes, is that bettas suffer from a fairly common eye disease called Popeye. For more information on this disease refer to our post Important Tips About Betta Fish Popeye.

Betta Anatomy - Internal View
Betta Anatomy -- Internal View



The mouth of a betta fish is lined with tiny and extremely sharp teeth on their lower jaw which helps the fish break down food before swallowing. Bettas have an upturned mouth which allows them to suck air, eat their prey at the water’s surface, and build bubble nests for their eggs. The mouth also serves a nobler cause. During mating, the male betta will suck up the eggs, and then spit them into the bubble nest where they will be fertilized. Due to their upturned mouths, some bettas may look like they have a smug face. What do you think? 🙂


A beta’s “beard” is a membrane, which is found under the gill plate cover. When the gills are closed, this membrane kinda looks like a beard. Male bettas will often open their gill plate and membrane to other betta’s, in an attempt to scare any foes. (For more on the differences between female and male betta fish -- refer to our post “Can You Tell the Difference between A Male and Female Betta Fish?“). Since I’m a huge fan of watching informational videos, I thought I’d share this interesting video that I came across where you can see this happen:

Betta fish flaring for the camera

I think I’ve covered most of the betta fish anatomy, but if you think I’m missing something important, please let me know and I’ll add it! Thanks for tuning in.

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