Betta Fish Swim Bladder

The Betta’s body weighs slightly more than the volume of water it displaces, so it tends to sink. So, like many other fish, the Betta has a gas-filled swim bladder that functions as a flotation device.

By making minor adjustments to the gas pressure inside the swim bladder, the Betta can remain suspended (neutrally buoyant) with little or no effort. If the Betta moves to the bottom of the tank, its swim bladder will be compressed and it will begin to sink. To correct this problem, the Betta must either add gas to its swim bladder to achieve neutral buoyancy again, or use energy to swim upward.

The opposite is true when the Betta moves toward the top of the tank. There, it must release gas from the swim bladder or must use energy to return to a deeper depth. Gas enters or leaves the swim bladder via a specialized duct. As the Betta moves about in its watery realm, small changes inside its body, unseen by the human eye, automatically maintain the proper buoyancy.