Does your tiger barb swim desperately to get deeper into the tank only to bob right back up to the surface? More than likely, a malfunctioning swim bladder is keeping your pal perpetually buoyant. A fish that struggles to submerge or stay afloat needs immediate care. Causes
The swim bladder is a gas-filled organ whose only function is to keep your finned friend buoyant and upright while swimming. If your fish can't control the amount of gas in the bladder, he may find himself hovering helplessly at the water's surface. Or if the bladder remains empty, your fish will sink immediately to the tank's bottom when he stops swimming. Either of these problems can keep your pet from snatching food, which can lead to starvation.
Causes include viral infections, fluke, roundworm and protozoa infections. Diseases such as vibriosis and mycobacteriosis (tuberculosis) can also cause swim bladder problems. Secondary bacterial infections cause thick, heavy secretions and a thickening of the bladder wall, which affect the bladder's ability to inflate and deflate.
Fish can also develop gas-bubble disease, a rare condition in which an overabundance of gas in the water leads to excess gas in the swim bladder. This causes fish to bloat and lose their ability to submerge. Tumors and cancers of the swim bladder can also lead to buoyancy problems. What You Can Do
You can prevent many fish diseases by maintaining a healthy aquarium ecosystem. Check for excess algae growth or a malfunctioning aeration unit, which might cause gas-bubble disease.