Gills are a fish's lifeline - they function as your finny friend's lungs, swapping carbon dioxide for oxygen. Any disruption of this vital process can cause death, so reddening or swelling of your fish's gill structures is cause for concern.


The gills respond to infection, irritation, or trauma by secreting protective mucus or thickening the gill surface, which makes it difficult for your pet to breathe. Fungal infections, such as ich (white spot disease) is a common culprit. In addition, bacterial and viral infections as well as parasites, such as gill flukes, can affect your fish's gills and, thereby, interfering with their ability to breathe.

Water quality problems can also cause breathing difficulty. Elevated levels of ammonia inflame gill surfaces, and nitrite poisoning prevents the gills from picking up oxygen.

Holding fins close to the body, rapidly flaring the gill cover, staying near the surface, and lethargy are hallmarks of gill and respiratory troubles.

What You Can Do at Home

Regardless of the cause, your pet needs immediate care to survive. The first thing you should do is test the water for common problems, such as ammonia, nitrite, and pH imbalances. Gill structures also are very susceptible to heavy, metal pollutants (such as copper and zinc), so you should analyze the water for these elements as well. Your local aquarium store or exotic animal veterinarian can perform the tests if you don't own a test kit. Also, make sure the aquarium's heater and air pump are working properly.

Next, change 25-50 percent of the tank's water and siphon debris from the gravel to increase filtration. Be sure to dechlorinate the fresh water and match its temperature and pH to the tank water. This simple routine will dilute any pollutants or disease-causing organisms in the tank.

When to Call Your Veterinarian

If your water analysis doesn't indicate any problems, consult with a fish veterinarian right away. The veterinarian may examine your fish, recheck your water parameters, take a thorough medical history, and recommend appropriate tests.

If you can't find a fish veterinarian in your area, consult with local pet store employees. And remember: quick action may save your fish's life.