Why Does My Betta Keep Sinking. The swim bladder is an organ in your fish that fills with gas to control buoyancy. Temperature shock is very common in betta tanks that don’t have heaters.
You need to do large water changes till you can get ammonia to under 0.25ppm. Swim bladder disorder (also called sbd, swim bladder disease, or simply swim bladder) is an extremely common disorder among bettas and other fish, particularly due to husbandry misconceptions. Consequently, why does my fish keep sinking?