fish diseases
Fish diseases are often tough to diagnose. The main categories are discussed in the tables below. Most progress rapidly, and the early symptoms are tough to tell on the fishes' small and constantly moving bodies. Any significant change in fish appearance or behavior should alert you to the presence of a disease. The key to treatment is catching early symptoms, isolating the affected fish in a quarantine tank, and medication. With worms, however, it's usually better to treat the entire tank than isolating the one or two fish that show signs of being affected. Read some sickness and nursing guide points, and scan the information below to identify the cause and remedy for your fish's condition.
This page does not need you to know any of the fin names, but if you need them for elsewhere, just hover your mouse on this picture.
Remember to remove the charcoal filter if you are ever adding medications to the tank, as it will prevent them from working by simply removing them from the water.
| Disease and Symptoms | Picture | Notes |
|---|---|---|
| Ich White spots (more like dots) on body or fin; Fish rejects food; Abnormal hiding; Fish deliberately scrapes against objects; Heavy breathing |
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A very common disease. Prognosis can be good. Quarantine immediately. Raise temperature to 85°F. Add aquarium salt. Don't use pure malachite green (sometimes recommended) as it is a toxic carcinogen, and stains acrylic tanks and fixtures. Use medicines like Rid-ick, which are based on substances like malachite green, methylene blue and quinine hydrochloride. Conduct daily 25% water changes (disrupts protozoan lifecycle) in the quarantine tank. |
| Velvet Velvet-resembling fine/tiny colored spots (can look like powder sprinkled on the skin); Fins held close to body by fish; Rapid swimming and scraping against objects; Heavy breathing |
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Also called Gold Dust disease or Oodinium. Prognosis can be good. Extremely contagious, and similar to ich. Quarantine immediately. Treatment similar to that of ich - raise temperature (85°F), add aquarium salt, use Rid-ick or other similar medicine (based on malachite green, methylene blue or quinine hydrochloride). Daily 25% water changes. |
| Neon Tetra Disease Restless, uneasy fast-pacing behavior in fish; Lone, separate behavior in normally schooling fish; Coloring of the fish fades; Spine tends to curve; Inability to swim straight (possible corkscrew motion) |
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Tough to diagnose in initial stages. Quarantine immediately (usually found in new fish, so always quarantine newly acquired fish). Always fatal, so consider humanely euthanizing the fish. Can affect fish other than Neon Tetras (e.g. Goldfish, Cichlids, Angelfish and others are also vulnerable). |
| Disease and Symptoms | Picture | Notes |
|---|---|---|
| Fin Rot One more more fins, or the tail, look eaten away, usually with a white edge at site of injury |
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Fin rot can be caused by bacterial (ragged fin, no white edge) or fungal (uniformly eaten fin, white edged) infection, and both can occur simultaneously in a fish. Prognosis can be good. Fins can be regenerated, unless the rot has reached the base of the fin (in which case the fin is usually lost forever). In early stage, treat with a combination of Melafix and Pimafix. In later stages, treat with Maracyn and Maracyn-Two combination. |
| Disease and Symptoms | Picture | Notes |
|---|---|---|
| Dropsy Swollen body; Bulging abdomen; In advanced cases, scales stick out to make the fish resemble a pinecone when viewed from the top |
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An internal bacterial disease. Abdominal fluid build-up (called "oedema") causes severe bloating. Quarantine immediately. Slow disease progression by raising tank temperature to 85°F. Feed medicated pellets if fish is eating. Dose water with Maracyn-Two. Prognosis poor, unless quarantined and treated prior to "pinecone" stage. |
| Popeye Eyes protrude, sometimes grotesquely; Cloudiness in eyes as infection spreads |
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Quarantine immediately. A good confirmation test to distinguish from injury is to see if both eyes are affected (could be to differing extents). Use Maracyn-Two. |
| Columnaris Sometimes starts with ragged fins, similar to fin rot; White fuzzy spots (larger than ich) on fish, sometimes around the mouth or side of fish; In later stages, a saddle shaped white area on the back (around the dorsal fin); Refusal to feed; Listlessness in the fish |
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Also called body fungus, as the white fuzz deceptively resembles a fungal infection. The bacteria is ever-present in tank water, and infection happens due to weakened immune system. Extremely contagious - quarantine immediately. Try medicated pellets if fish will eat. Dose water with Maracyn Two, and add aquarium salt. Lower temperature to 67-70°F, as heat helps bacteria grow faster. Add an airstone (airpump $10, tubing $4, airstone $0.50) to increase water oxygenation as that inhibits bacteria growth. Prognosis is poor, and most fish die within 4 days of appearance of white patch. |
| Fin Rot One more more fins, or the tail, look ragged and torn away |
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Fin rot can be caused by bacterial (ragged fin, no white edge) or fungal (uniformly eaten fin, white edged) infection, and both can occur simultaneously in a fish. Prognosis can be good. Fins can be regenerated, unless the rot has reached the base of the fin (in which case the fin is usually lost forever). In early stage, treat with a combination of Melafix and Pimafix. In later stages, treat with Maracyn and Maracyn-Two combination. |
| Tuberculosis No distinct symptoms in initial stages; Wasting away of fish; Ulcers and cysts in later stages |
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Extremely difficult to treat, with close to universal fatality. Quarantine immediately, and consider humane euthanization of the fish. Can spread to humans, so never put your hand unprotected in the tank if you suspect tuberculosis. |
| Septicemia Bloody (red or pink) blotches or streaks on body or fins; Often starts at the base of pectoral fins (side fins behind the head) |
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Quarantine immediately. Feed medicated pellets (such as Jungle Labs Anti-Bacteria Medicated Fish Food, $6 for 1 oz, crush pellets for smaller fish) if fish is eating. Dose water with Maracyn-Two (attacks the causative bacteria) and Maracyn (prevents secondary infection). |
| Disease and Symptoms | Picture | Notes |
|---|---|---|
| Whirling Disease Fish move in a corkscrew like motion; Deformities in younger fish |
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Caused by a microscopic parasite (myxobolus cerebralis) which causes neurological and skeletal damage. Very tough to treat. Quarantine and consider euthanizing the fish if it shows distinct advanced symptoms of this. |
| External Parasitic Worms Fish scrapes against objects; Fish darts around without apparent reason; Rapid gill movement, or gills held closed; Fins held close to body; Worms dangling from the body of the fish, e.g. near gills |
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Anchor worms and Flukes are often the worms involved. Quarantine not required, unless you just put the fish in the tank (i.e. worms may not have had the chance to spread in the tank yet). Separate and bathe the fish involved in potassium permanganate (40mg per gallon). Use anti-parasite tablets (e.g. Jungle Labs Tank Buddies Parasite Clear, $6) in the main tank. |
| Internal Parasitic Worms Worms dangling from the body of the fish near the anus (can look like poop dangling, but may be moving); Fish is thin |
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Threadworms are examples of this. Feed the fish anti-parasitic food (e.g. Jungle Labs Anti-Parasite Medicated Fish Food, $8 per bottle). Use anti-parasite tablets (e.g. Jungle Labs Tank Buddies Parasite Clear, $6) in the main tank. |
| Disease and Symptoms | Picture | Notes |
|---|---|---|
| Hole in the Head Disease Refusal to eat; Small grey pits near the head; As disease advances, pits ulcerate and spread down the body |
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Also known as Head and Lateral Line Erosion or HLLE. Unknown/debated cause (could be parasitic, autoimmune, water impurity induced, or microbial in origin). Only occurs in captive fish. Temporarily (for 4 weeks) increase weekly water changes to 25%. Be diligent about water changes. Improve fish nutrition with vitamin-enriched flakes, and once-a-week chopped garlic. Sometimes carbon in filtration is said to cause the disease - make sure you rinse thoroughly before you install carbon filter to rid of as much particulate carbon as possible. Try removing carbon filter for a month, with twice-weekly 15% water changes to substitute. Also, try anti-parasite tablets (e.g. Jungle Labs Tank Buddies Parasite Clear, $6). |
| Swim Bladder Disease Fish seems off-balance - tilted or even upside-down; Difficulty swimming |
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Cause is often difficult to pinpoint. Often a symptom of another problem, which should be identified by looking at any other symptoms the fish has. Can be caused by constipation also. Prognosis uncertain - depends on underlying cause. |
| Constipation Bloating of the body; Refusal to eat; Poop trailing behind the fish |
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Caused by too rich a diet or individual fish's genetic predisposition. Vary diet between pellets, flakes and freeze-dried worms. Vegetable matter (spirulina flakes or broccoli pieces) can really help. Soak food in castor oil before feeding. Do not overfeed. |