Specific signs of fish diseases.
Any disease is much easier to treat in its early stages. Therefore, noticing even the slightest deviations from the behavior characteristic of a given species, the physiological state of the fish, or minor changes in the outer body integuments in a timely manner greatly contributes to early disease diagnosis. This makes it possible to identify and isolate sick fish, thereby preventing the spread of contagious diseases and the death of the entire aquarium population. Close observation of fish is necessary, as they themselves serve as an early warning system for emerging diseases.
Characteristic signs of illness include refusing food, fading of body coloration, schooling fish separating from the group, impaired movement coordination, rapid breathing, and loss of response to stimuli. Bottom-dwelling fish swim near the surface or stay in corners, adopting a vertical position either head-down or head-up, or swimming in circles. Scratching against objects indicates ectoparasites on the body and gills. Serpentine swaying of the entire body points to low water temperature or ectoparasites.
If fish swim strangely, lose coordination, experience paralysis, exhibit spasms, dart around the aquarium in panic all or some of the time, breathe rapidly, swim to the surface and gasp for air, or if their gill color changes, this clearly indicates poisoning. These symptoms may appear individually or all at once. In many cases, fish die from the lingering effects of toxins quite some time after the poisoning occurred.
Activity levels in fish behavior.
It is very important to know what behavior is typical for a given species. For example, nocturnal fish may appear sluggish during the day, and vice versa. Some species of fish rarely show activity at all! Fish recently introduced into an aquarium are usually inactive for some time as a result of shock and stress. If left alone, such fish quickly begin to recover. Fish may become less active in old age.
However, if a fish becomes less active compared to its normal behavior, this is likely an early, albeit non-specific, sign of illness. Certain behavioral patterns in fish are usually indicators of disease. A fish should not dash about abnormally, stay in one place, hide, hang in a corner, or lie on the bottom. It is abnormal when a fish makes coughing, choking, or yawning movements; scratches; vibrates; loses coordination; tumbles; swims from bottom to top; or sinks. If several fish behave abnormally, this is a clear warning sign. A fish may swim head up or head down, stand in the corner of the aquarium, or hide to avoid aggression from other fish. Lethargy usually increases as the disease progresses and decreases as the fish recovers.
A newly introduced fish may initially be very restless and dart across the aquarium every time someone approaches it. Sudden movements near the aquarium should be avoided, and the fish should be checked for injuries. If almost all long-term residents suddenly start darting around, there is reason to suspect serious environmental issues or parasites. If only one or two long-term residents show such atypical dashes, changes in the social hierarchy or the onset of spawning activity should be suspected.
The circumstances under which a fish lies on the bottom play a crucial role in determining the cause of the problem. For newly introduced fish, the most likely cause is shock or stress. If all or many fish are affected, the problem is likely environmental. If only a single long-term resident is affected—one that was recently attacked by another fish, participated in a fight, courtship, or was handled—the problem is likely due to swim bladder trauma, exhaustion, or stress.
The fish constantly hides. For some fish species, this is completely normal behavior. Therefore, hiding is an instinctive self-preservation method. If provided with suitable hiding spots, fish will become bolder, feel secure, and leave their shelters more often than they would in nature. If nocturnal fish are kept, they are expected to hide during the day or at least remain inactive in a quiet spot. Newly introduced fish hide for a while until they recover from transport stress and familiarize themselves with their new surroundings.
Scratching is a consistent sign of irritation of one type or another. Sometimes a fish turns on its side and scratches. Occasional scratching should not be a cause for concern, but if one or more fish scratch repeatedly, it may indicate irritation caused by poor water quality, including suspended matter in the water. When fish scratch, it is most often caused by environmental issues or Ichthyophthiriasis. The cause quickly becomes obvious due to the appearance of characteristic spots on the fish.
• If the fish stays near the water surface with its dorsal fin protruding, accompanied by whitening of the skin around the dorsal fin and tail region — Pseudomoniasis.
• If the fish hangs head-up near the water surface with rapid breathing, this is a sign of Hypoxia. Such behavior can sometimes be observed in bottom-dwelling fish—usually cichlids—trying to escape an aggressor by moving to the upper water layers. The victim of aggression most often heads to a corner or the end of the aquarium where it feels relatively safer. At the same time, a fish experiencing hypoxia moves slowly along the water surface. Accelerated gill movement may indicate gill damage.
• If the fish is sluggish — Acidosis, Branchiomycosis, Gastrointestinal inflammation, Obesity, Cold-water disease, Tuberculosis.
• The fish becomes weak and is easily caught by hand — Diplostomiasis, Branchiomycosis.
• If the fish hides. If this is abnormal behavior for the species, it indicates that the fish is stressed, even if it is not actually sick. If left uncorrected, stress can cause serious health problems. Fish may hide if they feel unwell. This may be an instinctive reaction—the fish seeks to avoid predators and other troubles because in such a state it cannot perform normal evasive actions. A fish may hide because it is a victim of aggression. This situation can occur if fish with incompatible swimming habits are kept in the same aquarium.
Fish that dart frantically across the aquarium can be extremely restless neighbors. This rapid movement may be perceived by other fish as an aggressive threat or attack, and simply the fear of colliding with rushing fish can cause stress. A fish may hide when the lighting is too bright. Schooling fish can be nervous and hide if kept alone or in groups that are too small — Plistophorosis, False neon disease, Oodinium, Hexamitiasis, Chilodonellosis, Caryophylliasis.
• If the fish swims at an unusual angle: Loss of buoyancy or buoyancy control. As a rule, this is the result of swim bladder dysfunction. Movement coordination is impaired, and the fish swims sluggishly with jerky, spasmodic movements. The fish may swim head-down or tail-down, partially or completely on its side, or even belly-up. Plistophorosis, Ichthyosporidiosis, Pseudomoniasis, Caryophylliasis, Philometrosis, False neon disease. This indicates Trauma or a Bacterial swim bladder infection. Additionally, swim bladder dysfunction occurs in the late stages of Dropsy, Obesity, Malawi bloat.
• Adopting a vertical position, head-up, eagerly gulping air — Ichthyophthiriasis, False neon disease, Tetrahymenosis, Sanguinicolosis, Branchiomycosis, Bacterial gill disease, Dactylogyrosis. Fish often swim or hover head-up near the water surface where oxygen content is higher.
• If the fish swims head-down — Gyrodactylosis, Plistophorosis, Pseudomoniasis, Tuberculosis, which may indicate Stress arising from various causes.
• Swimming on its side — Acidosis, Tuberculosis, Branchiomycosis, Glugeosis, Gyrodactylosis, Ligulosis.
• Fish swimming belly-up is a secondary symptom for a number of diseases. You should closely observe the fish and determine the cause of the disease based on other symptoms.
• Outwardly healthy fish staying near the water surface upside down or on their side with a bloated belly — commonly found in goldfish as a result of improper feeding, such as a lack of required plant matter and ballast substances. A varied and balanced diet must be provided.
• If the fish lies on the bottom. For some fish—such as catfish and loaches—resting on the bottom or even lying on their side is completely normal. Some diurnal fish (e.g., cichlids) normally rest on the bottom after dark. In cases where bottom-lying is abnormal, it is often accompanied by respiratory distress. If many fish are affected, the problem is environmental. This may be — Temperature, osmotic, or nitrate shock, pH shock, Acidosis or Alkalosis, Hypothermia, Aeromoniasis, Chilodonellosis, Ichthyosporidiosis, Branchiomycosis, Swim bladder dysfunction, Dropsy, Malawi bloat, Tuberculosis, Saprolegniasis.
• Death occurs in plant thickets, with fish bodies curved into a ring, mouth and gill covers closed — Acidosis.
• If the fish dashes around the aquarium continuously. This should only cause concern if such behavior is abnormal for the species. If a fish lacks a personal safe refuge, it darts from place to place as quickly as possible to avoid potential or real danger. Atypically short dashes are sometimes associated with Poisoning, Elevated temperature, Acidosis or Alkalosis, Ichthyophthiriasis, External parasites.
• If the fish tries to jump out of the water — Aggression or fear of aggression, pH fluctuations, Alkalosis or Acidosis, Elevated temperature, Poisoning, Chlorosis, External parasites.
• If the fish makes serpentine swaying movements with its body, this indicates diseases caused by — Low water temperature, Ectoparasites, Gastrointestinal inflammation, Gyrodactylosis, Dactylogyrosis, Tetrahymenosis, Cold-water disease, Tuberculosis.
• If the fish swims in jerks and bounds — Ichthyosporidiosis, Tuberculosis, Oodinium, Hexamitiasis, Plistophorosis.
• If the fish constantly scratches and rubs against various objects. This is a sign of irritation due to poor water quality caused by skin or gill parasites, including Ichthyophthiriasis, Ichthyosporidiosis, Gyrodactylosis, Chilodonellosis, Dactylogyrosis, Diplostomiasis, Costiosis, Oodinium, Trichodiniasis, Tetrahymenosis. This indicates ectoparasites on the body surface and gills such as Lernaeosis, Argulosis. The cause quickly becomes obvious due to the appearance of characteristic spots. Water quality should be checked first, followed by parasite treatment.
• If the fish has spasms. Movements where the fish arches its body from side to side while remaining stationary, shakes its head, and yawns. Such movements can be nearly continuous or alternate with normal behavior. This is a sign of irritation associated with — Environment, Chemical composition changes, Poor water quality, High levels of nitrites and other toxic substances, Alkalosis, Trichodiniasis, Hypothermia. The problem can usually be resolved by a partial water change. — Infection caused by Flexibacter bacteria.
If the fish has jumped out of the aquarium.
This should be avoided, so the aquarium must always be kept tightly covered. Nevertheless, such incidents sometimes happen. Some fish can find any opening, no matter how tiny. Some seek freedom when the aquarist removes the lid to perform maintenance procedures. Some fish can jump right out of the net.
• If the fish was out of water for a short time, it should be gently rinsed in a bucket of aquarium water to wash off dirt and dust. All surface wounds should be treated with a topical antiseptic, and the fish returned to the aquarium. This avoids the additional trauma the fish might experience if moved to an unfamiliar quarantine tank. Most of the time, the fish looks a bit battered afterward but recovers without further treatment.
• If the fish remained in the air for some time (several minutes, even an hour or more), it can sometimes be revived in a hospital tank with good water aeration. Gently holding the fish underwater over an air diffuser helps clear its gills of dried mucus and floor dust. Skin damage, as in the previous case, should be treated with a topical antiseptic. The fish must be kept in quarantine for at least a few days to recover from the stress and hypoxia it experienced.
• In all cases, monitor the fish for signs of secondary bacterial or fungal infections.
• If the fish has internal injuries and shows no signs of improvement after a couple of days, euthanasia may be necessary.
Activity during feeding.
Appetite. Should show activity during feeding. True emaciation is indicated by a concave abdominal profile.
• If the fish is too thin — this is a secondary symptom for most diseases. You should closely observe the fish and determine the cause of the disease based on other symptoms.
• Refusal of food, loss of appetite, weight loss, sunken belly — a secondary symptom for most diseases. Branchiomycosis, Dactylogyrosis, Ichthyosporidiosis, Costiosis, Plistophorosis, Tuberculosis, Trichodiniasis, Chilodonellosis, Hexamitiasis, Gyrodactylosis, Aeromoniasis, Cryptobiosis, Caryophylliasis, Philometrosis, False neon disease, Camallanosis, Hypothermia.
