Disease & parasite cards

Practical cards from hobbyist practice + parasite chart. Doses and protocols on Treatments.

Parasite chart · Ich · Velvet · Costia · Chilodonella · Trichodina · Skin flukes · Gill flukes · Anchor worm · Lice · Columnaris · Aeromonas · Dropsy · Floating · Mycobacteria · Other

Parasite ID chart (skin)

Adapted from Scott P.W. (1985) in Manual of Exotic Pets, revised edition (ed. J.E. Cooper, M.F. Hutchison, O.F. Jackson, R.J. Maurice), BSAVA Publications. Use with a microscope when possible.

Speed of killers (order as listed on the chart above — treat fast killers first)

1. White spot (Ich)
2. Costia
3. Chilodonella
4. Gill flukes
5. Trichodina (if numerous)
6. Skin fluke
7. Lice
8. Anchor worms
9. Leeches

Ich (white spot)

• Symptoms: Salt/sugar-grain white spots; may form slimy masses when severe.
• Likely causes: Ichthyophthirius; often after temperature swings or stress.
• Check: Temp stability; ammonia/nitrite; nets/equipment hygiene (sticky tomonts).
• Treatments: Formalin/malachite green products on a multi-day schedule with water changes; some keepers used 3% salt dips + daily treatment while warming gently (~72–74°F). Cycle length is temperature-dependent (~days at warm temps, weeks when cold).
• Cautions: Feeding stage under skin resists meds; free-swimming stage is the target. Harsh baths on fried gills are dangerous. Disinfect nets. Verify current product labels.

Oodinium (velvet)

• Symptoms: Lethargy, flashing, dry patchy skin, yellowish dusty look, heavy slime.
• Check: Flashlight at night near dorsal fin; scrape if available (~200×).
• Treatments: Water changes, salt dip, formalin/malachite-type courses (~3 days).
• Prevention: Quarantine new fish; improve organics/water quality.

Costia (Ichthyobodo)

• Symptoms: Flashing; tiny red hemorrhages under chin / along back; thick slime.
• ID: Fast jerky motion; comma/kidney shape; high power for flagella. Divides quickly ~75–78°F; die-off ~86°F.
• Treatments: Salt dip to strip slime → multi-day formalin/malachite-type treatment → some protocols then warm carefully. Rule out bacteria if red dots are under scales.
• Caution: Heat without clearing other parasites can worsen mixed infections.

Chilodonella

• Symptoms: Clamped fins, gasping, lethargy, hiding, thick slime.
• Notes: Cooler-water problem (winter ponds). Rule out pH first.
• Treatments: 3% salt dip then formalin/malachite-type course with daily partial changes; ponds: therapeutic salt (see corrected table — weigh; do not guess tsp as %).

Trichodina

• Symptoms: Often tied to thick slime / degraded water; spinning “saucers” on scrape.
• Treatments: Clean water first; salt dip; formalin/malachite-type treatment.
• Note: Conditions that over-stimulate slime can increase numbers.

Gyrodactylus (skin flukes)

• Symptoms: Flashing, listless, frayed fins, thick/rough slime; common on peduncle.
• Biology: These flukes give live birth; worse in warm water and poor conditions. Most fish carry a few.
• Treatments: Praziquantel per label. Salt dips + PP or formalin/malachite are also used, as are very short dilute H₂O₂ dips (high risk — see treatments page).
• Support: Light salt to support slime (mass-based dose).

Dactylogyrus (gill flukes)

• Symptoms: Early — dark red at pectoral bases; later gasping, flared/gloppy gills.
• ID: Four eye-spots; ~100×. Egg layers — retreat/recheck over weeks (hatch ~4 days near 68–70°F).
• Treatments: Praziquantel per label. Salt dips + PP/formalin-malachite are also used (resistance reported); short H₂O₂ dips (dangerous). Bucket-to-bucket moves help leave eggs behind.
• Critical: Do not blast heat for bacteria until gill flukes are addressed.

Lernaea (anchor worm)

• Symptoms: Visible worm with forked tail embedded in muscle.
• Treatments: Remove with tweezers; treat wound topically (antibiotic cream). Ponds: insect growth regulators (availability/legality vary) on a multi-week schedule. Tank outbreaks: strip décor, dry equipment, rotate hospital water daily ~10 days to beat eggs.
• Note: Wounds seed secondary bacteria/parasites.

Argulus (fish louse)

• Symptoms: Flat round ~1/8"; dark eye spots; blood-sucking wounds.
• Treatments: Manual removal + topical wound care; same class of pond arthropod treatments as anchor worm where legal/available. Eggs on décor ~month later — environmental control matters.

Columnaris

• Symptoms: White threads at mouth; dry skin; darkening; cottony/thready sores; peduncle disease; red anal vent; sometimes chronic bubble-eating / balance issues from internal adhesions.
• Check: Mouth & vent; slime “dry”; gill patches; organics/feces load. Often follows parasites + dirty water.
• Treatments: Improve water; topical wounds; medicated foods; potassium permanganate water treatments for external disease (see treatments); injections only via vet.
• Internal: Water antibiotics often weak; food or vet route usually preferred.

Aeromonas / red sores (“spring crud”)

• Symptoms: Red sores (often white edge / red center); blood at pectoral bases for internal infection; pond outbreaks as water warms.
• Check: Parasites almost always present on pond fish — treat parasites before or with care around heat.
• Treatments: Clean wound (peroxide once carefully away from eyes/gills), topical cream; raise immune function with warmth only after parasites addressed; antibiotic food; injectables are vet procedures.
• Note: Many Aeromonas strains dislike high heat (~84°F); exceptions exist. Oxygenate heavily.

Dropsy (symptom complex)

• Looks like: Pinecone scales and/or ascites (swollen, scales flat) and/or bilateral pop-eye.
• Causes: Bacterial, parasitic, viral, toxic water, temperature shock, electrolyte/kidney failure — not one disease.
• Check: Full water panel; physical exam; scrape for parasites; single vs both eyes.
• Common treatment themes: Hospital tank; treat parasites first; little/no NaCl; small Epsom dose (e.g. 1/8 tsp per 5 gal — do not escalate blindly); high aeration; warmth ~84–86°F for weeks in bacterial cases; antibiotic food; move to fresh water regularly.
• Why heat fails: untreated parasites explode; too much NaCl; toxic source water; temp raised too slowly (selects hardy bacteria); toxic useless meds; starvation; stopped too early; untreatable primary cause (e.g. kidney failure / mycobacteria).
• Prognosis: Earlier = better. Ascites with flat scales + no ammonia production often worse (kidney).

Floating / “swim bladder”

• Common causes: Dry floating pellets / gulped air, constipation, egg-bound females, toxins (H₂S from gravel), adhesions, rare true bladder damage, gas-forming gut infection.
• First steps: Soak/sinking food; greens/peas; short fast if otherwise healthy on physical; Epsom-in-pea carefully; check gravel/anaerobic pockets.
• Not folk remedies: We do not recommend floating garlic or superstition-based “cures.” Address feed method, constipation, water, and infection differentials.
• Aggressive methods: Shallow recovery tub, walk the fish upright, heat + Epsom without NaCl, antibiotic food if enteritis/eggs suspected — ammonia monitoring mandatory.

Mycobacteriosis (fish TB)

• Typical picture: Chronic lethargy and appetite loss; fish may waste over weeks despite clean scrapes and multiple failed OTC antiparasitic/antibiotic courses. Internal granulomas (often acid-fast bacilli consistent with Mycobacterium sp.) are a known differential; secondary environmental bacteria can coexist.
• Hobby takeaway: There is no reliable over-the-counter cure. Endless med stacking rarely helps and delays proper decisions.
• What to do: Isolate affected fish; gloves and hygiene (zoonotic potential); escalate to an aquatic veterinarian (diagnostics / euthanasia decisions as appropriate); do not reuse untreated filter media across tanks carelessly.

Other cards (short)

Acidosis (low pH)

Gasping, darting, thick slime, dark gills. pH crash from organics / biofilter death. Raise pH slowly with matched water; aerate; clean organics; buffer (crushed coral / dolomitic lime — not sudden slaked lime). Avoid harsh meds on fried gills.

Alkalosis / high pH + ammonia

Darting, gasping, red streaks, sudden death. Ammonia more toxic at high pH. Common in cycling tanks or leaching concrete. Lower pH gradually; frequent changes until cycled.

Rockitis

Yawning, head-standing, imbalance — gravel stuck in mouth. Remove with rounded tweezers; use gravel too large to swallow or bare-bottom feeding zones.

Hexamita / hole-in-head style lesions

Lateral-line pitting, depigmentation, white threads. Nutrition/stress/mineral theories; metronidazole is used (food preferred). Improve diet and water; reconsider carbon media if suspected contributor.

Skinny disease

Big head / sucked-in look while still eating. Erythromycin-in-food courses are used; also rule out parasites and mycobacteria if chronic.

Black spot (digenean)

Vs ammonia-burn black marks (healing). Needs snails in life cycle. No great OTC kill of encysted metacercaria; manage snails; salt + clean water for secondary infection risk when cysts erupt. Copper only with correct hardness/pH.

Epistylis / carp pox / lymphocystis

Wart-like or greasy buff growths. Clean water; formalin-type products for epistylis; viruses often wait-and-support.

Branchiomycosis

Mottled / bluish-gray gill streaks in hot, organic, low-O₂ water. Hard to treat; salt dips + mechanical removal of crud + antibiotic food + continuous fresh flow. Some koi lines salt-intolerant.

Brain / eye flukes

White fleck in eye, circling. No reliable treatment; eliminate snails.

Gas bubble disease

Bubbles in fins/skin from supersaturated gas (well water, pump leaks). Degas water; do not “medicate.”