Signs & Symptoms of Sick Goldfish

How do you know when your fish is sick?

If you see any of these 5 signs it’s an indication your goldfish is in distress.

These are some of the most common signs of disease in goldfish. The good news is that they can be treated quite easily. Getting to the cause of the problem and fixing it quickly is the key for a full recovery.

Symptoms of dropsy, white spot, ich, anchor worms, fish tail rot
a fantail with fins turning black

#1 Gasping for Air

What to Look For: Sick goldfish may often struggle to take in enough oxygen.

Fortunately it’s pretty easy to tell if your goldfish are gasping for air as they’ll usually stay around the surface, gulping down bubbles, or will swim in jerky patterns with their mouth open.

Cause: The good news is that gasping for air usually isn’t a sign of anything sinister, and it’s more often a symptom of stress. Stress itself isn’t dangerous for a goldfish, but it can reduce the efficiency of the immune system and leave your fish susceptible to disease.

Treatment: Look for common stress triggers in your tank that may be making your goldfish sick. This includes water temperature (keep it between 23 and 24 degrees celsius), cleanliness of the tank, overcrowding, even undercrowding, and air pump oxygenating the water.

# 2 Unusual Swimming Motions

What to Look For: Healthy goldfish will normally swim in an upright position, and will naturally position themselves nearer to the bottom of the tank.  This is because it’s instinct to protect themselves from predators. Sick goldfish, however, may swim sideways, tilted at a 45 degree angle, or can stay at the top of the tank. This is a sign that they’re unable to sink to the bottom.

Cause: Swim Bladder Disease is the most common reason for unusual swimming motions, although there are numerous other causes of the condition, including stress, parasites, or digestive problems.


swim bladder disease treatment for betta fish

Digestive problems are the most common cause of Swim Bladder Disease, as the swim bladder is connected to the digestive tract.

Try soaking dried food to soften it before feeding to reduce bloating, or give your sick goldfish daphnia which acts as a natural laxative.

#3 Visible Skin Issues

What to Look For: Sick goldfish may display a number of physical symptoms of disease, such as open wounds which can be white, pink, or red in color, a tightening of the skin which can suggest swelling, small spots that can be white or gold-like in color, frayed or ragged fins, or visible lumps or growths on the gills.

Cause: There are multiple causes of skin complaints in fish, so diagnosing sick goldfish through visible signs can be tricky. Small spots are likely to be parasites, perhaps Ich, while open wounds could be the sign of ulcers. Tightened skin could suggest Dropsy, while damaged fins are often a sign of Fin Rot, or of a bacterial infection.

Treatment: Skin issues can usually be treated in one of 3 ways depending on the cause. Anti-fungal medications, anti-bacterial medications, or heat treatments for parasites.

#4 Unusual Eye Appearance

What to Look For: Your goldfish may appear to have protruding, bulging eyes when sick which are very obvious to owners, but symptoms could also be much more subtle.

Keep a look out for excessive mucous build ups on and around the eye, or a cloudy film covering the eye. It can be difficult to see these symptoms.

Cause: Differences in the eye appearance of goldfish usually happen for one of 2 reasons. Exophthalmos of the eye, or ‘Pop Eye’ as it’s commonly known, is a swelling of the eye, and is usually caused by an infection.

Cloudy Eye, on the other hand, which may or may not be accompanied by swelling, is usually a sign of a vitamin deficiency.


  1. Goldfish that have been diagnosed with Pop Eye should be quarantined and treated with antibiotic medications prescribed by a fish veterinarian.
  2. Cloudy Eye can usually be rectified with a change in diet to include more vitamins, such as incorporating live food for example, or may even clear up with a change of water and better tank cleanliness.

#5 Refusing to Eat

What to Look For: Sometimes diagnosing sick goldfish can be similar to people, and a sudden loss of appetite is usually one of the first signs that something is wrong. Keep an eye out for food flakes that remain uneaten and are left to rot, and for sick fish who might not swim to the surface at feeding times.

Cause: A refusal to eat can be caused by something as simple as a small amount of stress because of a change in water, for example. But it could also be a sign of something more serious. Unfortunately diagnosing fish who aren’t eating can be difficult but it’s often a sign of ammonia toxicity. Too much ammonia for the size of the tank.

Treatment: If you have diagnosed ammonia toxicity, move your fish to a larger tank and install a heavy filtration system to ensure the water is kept clean. Properly oxygenated water is a necessity for your goldfish to grow bigger and live longer.

If you’re unsure why your goldfish is sick, look out for other symptoms that could point to what’s wrong.

Should I Self-Diagnose a Sick Goldfish?

One of the best aspects of owning goldfish over other types of fish is that they’re incredibly hardy and rarely become sick as long as they’re kept in an environment that suits their needs.

What’s even better is that if goldfish do become sick the more common goldfish diseases aren’t killers, and can usually be treated successfully at home.

This begs the question: ‘Is diagnosing sick goldfish at home a good idea, or is it better to get a professional opinion?’ Unfortunately it’s often difficult to tell what’s wrong with a goldfish (if only they could talk!), but some diseases are more obvious than others. If you’re in any doubt, always chat with your veterinarian. They’ll be able to suggest the best course of action for your sick fish.

While most people tend to think that cats and dogs have the best personalities, fish can also have some cute and very individual behaviors and tendencies.