How To Tell If Your Goldfish Is Sick: a Complete List of Symptoms

You may have noticed that your goldfish is no longer the same …And this could come as a real shock.

But what is happening to your fish?

You have come to the right place because I have made a complete list of symptoms.

Some are common, others not quite.

But you can find them all here.

WARNING! Before you read:

Even if you experience a symptom, your goldfish doesn’t necessarily feel bad.

Most of the time it is all the fault of the aquarium conditions … This is why in such cases it’s always better to check the water first.

Unusual behaviors

1) Goldfish gasp on the surface of the water (inspiring air): It can happen that a goldfish gasp as if it were ” drinking ” the air. Some dart to the surface, take a quick breath and go swimming again. This means that something is wrong with the aquarium, it’s usually the fault of the water. Perhaps the agitation of the water is not enough or the aquarium is not large enough to supply oxygen to the goldfish, although there is most likely an imbalance in the levels of nitrite, ammonia, or pH. Goldfish gasps at the surface of the water even when the gills are damaged by medicines bought at the pet store or by a parasite infestation.

2) Apathy: When a goldfish is healthy it spends most of its time swimming around without stopping and looking for food at the bottom of the aquarium. If it seems weak and inactive, this is not a good sign. In these cases, the fish stays at the bottom of the aquarium or near the surface with a slightly sluggish air, if another goldfish bites it and it does not care and in general it seems depressed. In cases like this, check the water as there is likely a sharp drop in pH or some other erratic parameter change.

3) Goldfish jumps out of the aquarium: Some people mistakenly call it “goldfish suicide”, but it’s actually an attempt to escape discomfort due to poor water conditions or parasites. Before doing so, the goldfish behaves in an unusual way: it swims quickly around the aquarium, rubs against the objects inside it, or writhes frantically and, due to all these stunts, sometimes ends up on the floor.

The problem is not always water or a disease: sometimes, when males chase them in the breeding season, female goldfish jump out of the aquarium and try to escape. In the event that a particularly aggressive specimen makes the others jump out, try to isolate it from the rest of the aquarium. If you find a goldfish on the floor, don’t be discouraged! Once in the water, they can recover as long as they are not completely dehydrated, and less than an hour has passed.

If the gills have closed, you can gently reopen them with your nails. A tiled or wooden floor gives runaway fish a greater chance of survival as the water it carries with it stays longer than on the carpet. Do not return the goldfish to the aquarium if its eyes are sunken or gray (this indicates that it is dead) if the skin creaks or has been injured. 

How To Tell If Your Goldfish Is Sick: a complete list of symptoms

4) Goldfish Stays at the Bottom of the Aquarium: If the goldfish appears to be resting at the bottom of the aquarium it probably has something wrong with it. A healthy goldfish is almost always on the move; if not, check your aquarium. In these cases, the fish lies on its side, has stiffened fins, or shows some other symptoms related to a health problem.

If It has a red belly there is usually nothing more to be done. But why do goldfish behave like this? The problem is usually the quality of the water, but sometimes the cause is a pain in the swim bladder due to constipation.

A goldfish in these conditions, if frightened, spins at the bottom of the aquarium while when suffering from nitrite poisoning it gathers its strength and continues to swim regularly. If your goldfish is constipated, try feeding it frozen peas for a few days until It resumes swimming as before.

5) Goldfish dart around the aquarium: A goldfish is said to ” dart ” when it swims around the aquarium out of control, turning on itself to rub the surface, skidding against the aquarium decorations, or colliding on the corners of the tank.

You might think that everything is fine, but if a goldfish does that it means that it’s itchy, a bit like being bitten by a mosquito. In these cases, the goldfish swims without any control and it’s better to intervene. It may be itchy, but your goldfish may be harboring some pathogen. The presence of ammonia, nitrite, and chlorine p can also be the cause, as well as a drop or increase in pH.

6) Spasms/jerks: If the goldfish suffers from severe irritation, it jumps frantically: it can suddenly shake its head from side to side, shake its whole body or its fins. This symptom is mainly due to water conditions, however, pest infestations can cause even worse irritation.

How To Tell If Your Goldfish Is Sick: a complete list of symptoms

7) Stiffened fins: Goldfish tend to stiffen their fins due to any problem related to water quality and for almost all types of parasites: in these cases, it swims as if wearing a very tight jacket, with the fins that adhere to the body as closely as possible. Sometimes the fins fidget nervously or have worthy spasms.

As when it whizzes here and there it’s a sign that something is wrong. The causes can be found in the amount of ammonia or nitrite in the water, but often stiff fins are due to infections of parasites such as Ichthyophthirius multifilii , fasciole, fish lice, and velvet. Remember: always check the water before trying to identify a disease.

8) Rapid/fatigued breaths: By observing the movement of the gills you can identify any breathing problems. When goldfish breathe quickly, they usually suffer from a lack of oxygen. If you keep your fish in a bowl (which is absolutely wrong; read the Common Mistakes section) there is no agitation of the water nor enough volume of water to allow it to breathe, so the fish will struggle to keep up.

sufficient oxygen levels. In this case, move your goldfish to a larger aquarium as soon as possible. Accelerated breathing could also be a sign of stress, especially if the fish remains at the bottom of the tank. Stress may be due to moving to a new habitat after a long drive from the pet store. Sometimes during the breeding season the stress of the female specimens, exhausted after being chased by the males for hours, increases.

But stress is also caused by poor water conditions or disease, so always check the quality of the water; if you do not find any problems, the problem may be the fasciole or any other parasite. A goldfish that has difficulty breathing may clear its gills by repeatedly “yawning”.

9) Goldfish Swims Up and DownDoes your goldfish seem to be having difficulty maintaining balance? Usually, when goldfish swims up and down they have problems with their swim bladder – the organ that controls their sense of direction.– generally due to an intestinal blockage.

This means that the meals are too large or too frequent, or consist of a single dish. Feeding It peas usually solves the problem. But buoyancy is not always a symptom of a swim bladder disorder. A high amount of nitrite or the presence of ammonia in the water can cause problems for the fish when swimming. If, on the other hand, it is attacked by internal parasites, it loses its appetite and fasting leads it to float or capsize.

10) Goldfish hangs on one side: If your goldfish hangs slightly on one side it can be a natural behavior, especially when they don’t have the backbone to help them keep their balance in the water. If you find it also very thin it may be due to a high concentration of nitrites in the water.

How To Tell If Your Goldfish Is Sick: a complete list of symptoms

11) Refusal of food: When a goldfish is healthy it consumes anything edible, leaving no leftovers. If, on the other hand, It gorges Itself on food and then discards it in a cloud of small pieces, it means that there is some problem.

Stress can prevent goldfish from swallowing food, and this usually happens to specimens that have just been brought home from a pet store and need to settle in. Other causes could be an infestation of gill bundles or decay of the mouth.

Additionally, a goldfish suffering from advanced dropsy (a buildup of fluids within the body) cannot swallow food. If a fish is too sick to even eat euthanasia is the most merciful solution as otherwise, it could starve much more slowly.

Physical symptoms (by parts of the body)


1) Bulging eyes: If it seems to you that fluid-filled undertows surround one or both eyes, or that the bulbs are bulging unusually, most likely a bacterial infection is the cause. If the goldfish also has protruding scales (dropsy), then there is nothing more to be done and it is better to resort to euthanasia. An underdeveloped goldfish may have permanently bulging eyes due to its disproportionate growth.

2) Cloudy, whitish eyes: In these cases, the goldfish eyes resemble ice-encrusted glass. The fish has difficulty seeing food or bumps into objects. The cause may be a bacterial infection from a wound or a burn from ammonia or harsh chemicals contained in some medicinal products.

3) Eye Loss or Injury: Sometimes a goldfish can injure its eye from cutting itself against an aquarium decoration, from being injured by another fish, from infections, or from chemical burns from water toxicity. In some cases, the goldfish can completely lose its eye and remain blind from that socket.

This happens easily to telescope goldfish given the size of their eyes. Fortunately, most goldfish are able to heal themselves and can continue to live peacefully. With this in mind, it is important to choose suitable decorations for your aquarium and to keep the water in good condition.

How To Tell If Your Goldfish Is Sick: a complete list of symptoms

The Gills

1) Red gills: It happens that those who have a goldfish get alarmed by seeing that the gills are red, but there is no need to worry. It’s easier to see the red color in the gills especially if the fish is white or dull in color. If the gills are swollen or remain open, however, it could be the fault of the fasciole or bacterial infection. Salt can be an effective solution against fasciole, and the same goes for almost all parasites.

2) Pale gills: As mentioned, the gills of a healthy goldfish should be bright red, while when they are pale or whitish it is a symptom of a disease. Parasitic infections such as those of the fascicles can cause microscopic gill hemorrhages that lead to loss of color.

3) Holes on the surface of the gills: This is the symptom of serious bacterial infection: it can be resolved with injections of antibiotics which, however, will not close the holes.

How To Tell If Your Goldfish Is Sick: a complete list of symptoms

The Mouth

1) The mouth remains wide open: Sometimes a piece of gravel can end up in a goldfish’s mouth while it’s eating food at the bottom of the tank. It usually manages to expel it in a day, but first, It will swim with Its mouth wide open and look different than usual. If after 24 hours there is no improvement it’s recommended to extract the gravel from the body of the goldfish.

Gently squeeze it in one hand while holding tweezers in the other, press under your chin and use the tweezers to very gently remove the piece of gravel. In some cases, the mouth of the goldfish can remain wide open without any gravel inside, and then close on its own and return to the same position when the fish reopens it.

This is a very rare phenomenon, due to stunted or disproportionate growth from being kept in too small an aquarium for too long. In this case, the fish will not be able to eat and will die of hunger unless it is done first with euthanasia.

2) The mouth opens on one side only : This is actually not a symptom of a water disease or problem, but a genetic defect: the mouth is small and sometimes bent at an angle to one side or even inverted. Goldfish in these conditions should be served food in smaller pieces than other aquarium fish.

3) The mouth is red: When the mouth shows signs of redness and inflammation or begins to disintegrate, it’s gangrene. The fish may rub their mouths on the aquarium walls or decorations thus causing irritation. Even blisters can form. Mouth gangrene in goldfish is a serious problem and develops very quickly, so it needs to be addressed immediately.

How To Tell If Your Goldfish Is Sick: a complete list of symptoms

The Skin

1) Black spots or streaks: If natural changes in pigmentation occur, a goldfish’s scales, head, or fins may blacken, as can a recent wound healing. As a goldfish ages, the colors can change in unexpected ways. We only need to worry if the black marks recur cyclically, in this case, the problem is related to water or to the attacks of another fish.

After an increase in ammonia occurs, the burns heal leaving black scars, but usually, the pigmentation returns to its natural color if the water conditions remain relatively stable. Sometimes, when the fins heal from gangrene, they are edged in black.

2) White Spots: If your fish appears to be covered in snowflakes or grains of sand, this is probably the cause. This protozoan is white in color and will multiply until both fins and body are fully dotted. Sometimes a single Ichthyophthirius multifilii can come and go attaching to a goldfish’s tail or cyst if its immune system is not functioning at full capacity.

3) Raised bumps: Abnormal bumps under the skin or attached to the scales are tumors that may or may not be cancerous. Tumors come in all shapes, sizes, and colors and can grow very large if left untreated. They manifest as white, pink, brown, or dark bumps. These clusters sometimes even appear on the fins as a result of the accumulation of toxins in the water. These tumors can be removed, but if left untreated the fish could die.

4) Red spots on the body: Usually these are ulcers or a sign of them. Ulcers develop from a small red patch of blood on the skin and progress until the skin begins to swell and erode. However, the red spots on the fish’s body can be signs of parasitic infection such as anchor worms or fish lice, so examine the fish closely.

5) A white or milky film on the body: This is due to the hyperactivity of the goldfish’s membrane producing excessive mucus in response to parasitic attacks or poor environmental conditions. Check for a pH swing and analyze the water for ammonia or nitrite. If there is no water problem, the cause is probably a parasitic attack. Fasciole and worms still cause goldfish to produce a whitish patina on the skin.

6) Paling: Usually when a goldfish loses its color it means that it’s unwell and is suffering from poor water conditions or an illness. If you find nitrites with a water test kit, you have probably found the cause of the color loss and need to take action to reduce it.

If you detect traces of ammonia or nitrite or if the Ph levels have suddenly changed, change half of the water immediately. Stress can also cause goldfish to lack brilliance for a period of time until they recover or the cause of the stress is eliminated, for example, a particularly aggressive aquarium companion.

If the immune system of the goldfish is attacked by some parasite the color can go from bright to off: any number of parasites can cause the shine of the scales to fade. To make sure your goldfish’s scales are always bright, feed them a quality diet that helps them regain color. Also make sure the aquarium is adequately exposed to light during the day (but not too much, you don’t want an algae infestation!). This will help keep the goldfish color on.

7) Inflammations: If red, painful and sometimes large inflammations appear on the body of a goldfish, they are ulcers, caused by bacteria that attack the skin when the fish’s immune system is inhibited, usually by poor water conditions. The ulcers continue to consume the goldfish’s skin until it can no longer resist and dies.

8) Fluff-covered patches: This could be a fungal or bacterial infection that develops cotton-like patches on the head, body or even fins that can be difficult to identify with the naked eye.

9) Worms that sprout from the body: These are anchor worms, a parasite that attacks fish at certain times of the year, but with some warning, they can be eliminated.

How To Tell If Your Goldfish Is Sick: a complete list of symptoms

Tail and fins

1) Traces of blood / red spots on the tail or fins: This is a clear sign that there is a problem in the water: a high amount of ammonia or nitrite can rupture blood vessels and cause bleeding in the tail veins. The result is red lines or bloodstains that appear on the fins. With water changes and a large enough aquarium, the healing of the goldfish is assured.

2) Tattered or frayed tail and fins: Excessive amounts of ammonia or nitrite can damage goldfish fins as if someone had chopped them up with scissors until the ribs look like spines. The fins also disintegrate when they are gangrenous. Another cause can be the Hexamita parasite, a protozoan that develops as a result of poor environmental conditions.

3) Tears/fractures in the tail or fins: If there are multiple goldfish in the aquarium, it can sometimes happen that they attack each other and fracture the fins. An aggressive goldfish may take another’s tail by the mouth and cause snags. Fractures can also be caused by poor water quality which could cause fractures in the thing. If the fins are worn it could be a sign of gangrene.

4) A milky film on the tail or fins: This is due to excessive mucus production, in response to poor environmental conditions or a parasite attack. This milky sheen can be easily spotted on goldfish varieties such as Black Moor.

The Excrements

1) Floating stools/air bubbles in stool: This happens when your goldfish’s diet is not varied enough. After many meals of dry food, air bubbles accumulate in the digestive system and are expelled with the feces. Normally a goldfish’s droppings are the same color as their food, usually dark brown, and sink to the bottom of the aquarium.

2) White, long, stringy stools: If the outside of the stool is hollow and stringy, this happens to goldfish in an aquarium with sand on the bottom, which means that there is a bacterial intestinal infection or that there is not enough food. (Sorry for the description)

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