Symptoms & treatments of aquarium fish disease

Fish diseases showing clamped fins and apathy

Symptoms include behavioral symptoms and physical symptoms. Take the time to check your fish behavior each day if possible as fish behavior can provide an early sign that something is wrong.

The symptoms in the table below are divided into 2 parts: common symptoms are preceded by the mention (1) and possible associated symptoms by (2).

Check the main symptoms first, then the other symptoms, which may help you to refine the diagnosis. Then click on the possible disease or issue link for a full description and treatment suggestions. Diseases and treatments apply to all freshwater fish. declines all responsibility in case of an incorrect diagnosis.


(1) bulging abdomen (swollen belly), raised scales ('pineconing').

(2) pale color, fish is listless. Loss of appetite, the affected fish isolates itself from the rest of the group. Sometimes, sores (reddened ulcer).
Dropsy: click here
Fish Pop-Eye:

(1) swelling of the eye, bulging eye(s)

(2) pale color, fish is listless. Loss of appetite, the affected fish isolates itself from the rest of the group. Sometimes, reddened ulcer.
Fish Pop-Eye: click here
Fish Fin rot:

(1) shredded or frayed tail or fins: gradual erosion of the fins, often the caudal fin (tail), which appear as 'eaten', torn. Fins sometimes display opaque or whitish edges.

(2) pale color, apathy, loss of appetite, the affected fish isolates itself from the rest of the group. Sometimes, reddened ulcer.
Fin rot: click here
Fish Cloudy Eye:

(1) The surface of the fish eye becomes cloudy almost to the point of whiteness and the fish loses vision from that eye.

(2) swollen eye, pale color, apathy, loss of appetite.
Cloudy Eye: click here
Fish White Spot Disease:

(1) fish appears to be dusted with small white dots (about 1mm, the size of grains of fine salt or sugar.

(2) rapid / labored breathing in the event of a heavy infestation (damage to the gills). The fish may stay just below the surface, gasping at the surface of the water. Sometimes, presence of a white, milky film on the fish body (production of excess mucus in response to the threat of parasites). Darting and scratching: the fish may rub against the stones or tank decoration. The affected fish may isolate itself from the rest of the group and display clamped fins.
Fish White Spot Disease
(ich) : click here
Fish Velvet Disease:

(1) tiny yellow or golden dots under normal or strong lighting (but almost greenish if the lighting is low). The skin of the fish takes the appearance of velvet. The dots, 0.10 to 0.25 mm are much smaller and tighter than for the white spot disease described above.

(2) respiratory problems (accelerated gill movements), redness and irritation. The fish sometimes rubs against the tank decoration and sometimes shows an unusual fearful character. Possible excess skin slime coat (excess mucus in response to the threat of parasites). Sometimes, clamped fins.
Velvet Disease (oodinium): click here
Fish Fungus Disease:

(1) development of filamentous or fluffy whitish or greyish patches
(2) Sometimes: fish is listless. Loss of appetite. The fish may rub against the stones or tank decoration.
Fungus - page coming soon
Anchor worm:

(1) Small parasites visible from 0.5 to 1.5 mm long (female size, only visible) and invading the skin and gills.

(2) The fish rubs against the stones or tank decoration. Fish is listless. Loss of appetite. Red and inflamed skin irritation. Respiratory problems (rapid or labored breathing) and even suffocation if the gills are infected. Sometimes, clamped fins.
Anchor worm : click here
Fish skinworms:

(1) Parasitic worms not directly observable to the naked eye . Fish with gyrodactylus skinworms rub against the scenery and appear to want to escape an invisible predator. Fish with the gill variety of the parasite have difficulty breathing (jerky movement of opercules, wide open.

(2) highly infested fish: sometimes hyper-secretion of mucus, bleeding of the gills, fearful or lethargic behavior.

Important note: the presence of ammonia or nitrite or a lack of oxygen can cause similar symptoms. Please check your water quality (ammonia, Nitrite and pH). This disease requires the observation of a sample under a microscope to be diagnosed with certainty.
Gyrodactylus skinworms: click here

Dactylogyrus gill worms: click here

(1) the skin becomes milky, covered with an opaque whitish to greyish coat.

(2) Fish rubs against objects. Respiratory problems, increase in mucus production, redness and sores, lethargy.
Costia : click here
Poor water quality or bacterial infection:

(1) your goldfish has difficulty balancing itself in the water the fish remains either at the bottom of the tank, unable to rise or, more commonly, stays close to the surface, unable to dive again.

(2) The fish may also swim on one side, unable to balance again. In extreme cases, the fish swims upside down (bellly up).
Bacterial infection: click here

Issue with water quality : click here
Various symptoms:

(a) Gasping. Fearful behavior, constantly rest on the gravel with clamped fins. Fish may become lethargic, feed little or not at all.

Other common symptoms include: veined or red spots on tail or fins, frayed fins, black smudges on fish skin, bright red gills with possible bleeding and rapid / labored breathing

(b) Simultaneous and unexplained death of several fish or unusual behaviour of several fish at once.

(c) Darting and scratching; the fish rubs against the decoration or stones, looks nervous, tries to jump out of the water or escape an invisible predator.

(d) lethargy and significant weight loss, low food intake, chronic mortality.
Ammonia or Nitrite poisoning : click here

Hypoxia (insufficient oxygen levels) : click here

Parasitosis (parasitic infestation), which can damage the gills
Missing or damaged eyesDamage due to mishandling, or a sharp object in the tank (avoid any sharp decoration, especially with fragile varieties like telescope goldfish).

Fish bullying

AttentionSick fish? Diseases are often an indicator of an imbalance in the fish tank. It is therefore recommended to test your water when you suspect a problem. This includes checking the ammonia and nitrite levels (should normally be at 0 mg/l). Water changes and maintenance are important, as an infection is much more likely if tank hygiene is poor. Other factors contributing to fish disease are: poor transport conditions or acclimatization, overcrowding.