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Uronema marinum (marine ciliate)

A scavenger ciliate that becomes pathogenic under poor water quality or stress, causing rapidly spreading open lesions, internal hemorrhaging, and fast death in marine fish. Fish appear to melt. Uronema is most dangerous to thin-bodied fish (chromis, small wrasses, clownfish) and is often introduced with uncleaned live rock or wild-caught fish. Notoriously difficult to treat.

Urgentpattern match not diagnosis1 source note

Do first

  • Move the affected fish to a hospital tank immediately.
  • Begin formalin treatment formalin is the most effective treatment for Uronema.
  • Correct water quality in the display tank Uronema thrives in poor conditions.
  • Act fast Uronema progresses from first lesion to death in as little as 24–48 hours in some cases.
  • Check all other fish in the tank for early lesions or red streaks.

Escalate if

  • Lesions spreading rapidly despite formalin treatment.
  • Fish listless and in severe decline prognosis may be poor; consider humane euthanasia.
  • Multiple fish developing lesions simultaneously outbreak management required.

Water clues

These readings can push this pattern higher or lower in the triage result.

ammonia above zero+5

Uronema is an opportunistic scavenger. Poor water quality is the most important predisposing factor.

nitrite above zero+4

Water quality stress increases the likelihood of Uronema becoming pathogenic.

Care protocol

Follow only the steps that fit your species, tank inhabitants, and medication label.

Identifying Uronema

  1. Uronema causes rapidly spreading open sores, often starting as a slightly red or pink patch.
  2. Lesions progress to open hemorrhagic ulcers that may look like the flesh is dissolving.
  3. Internal hemorrhaging may be visible through the skin in thin-bodied fish.
  4. The progression from mild lesion to death can be extremely fast.
  5. Distinguish from bacterial septicemia (red streaks without open lesions initially) Uronema causes lesions faster.
Cautions
  • Uronema can be on other fish in the tank without showing symptoms treat all fish if Uronema is confirmed.
  • Do not delay treatment for definitive identification.

Treatment protocol

  1. Formalin bath at 25 ppm for 30–60 minutes in a well-aerated container do not leave fish unattended.
  2. Continue with daily or every-other-day formalin baths while housing the fish in a clean hospital tank.
  3. High-salinity baths (briefly raising salinity to 35–40 ppt) can be used as an adjunct treatment.
  4. Metronidazole has been used with some success as a supporting treatment but is not the primary approach.
  5. Maintain treatment for a minimum of 14 days or until lesions fully heal.
  6. Clean the display tank water and check for and eliminate any organic waste accumulation.
Cautions
  • Formalin is toxic dose precisely and increase aeration during treatment.
  • Uronema treatment success rates are lower than for ich or velvet early detection is critical.
  • Do not return the fish to the display tank until lesions are fully healed.

Source notes

References and context notes used for this triage entry.

Uronema marinum in marine fishMerck Vet Manual reference for ciliate parasites in marine aquarium fish.
Run Symptom CheckerCompare this pattern against water readings, affected count, and recent tank context.Ask AdvisorUse TankFlare Advisor to review this against your saved tank and recent logs.

Related patterns

Similar symptoms or risk factors worth comparing before treatment.

UrgentBacterial septicemia (hemorrhagic septicemia)

Red streaking, hemorrhaging under the skin, and systemic illness caused by gram-negative bacteria (most commonly Aeromonas hydrophila) entering the bloodstream. Can follow injury, fin rot, poor water quality, or be primary in severely stressed fish. A systemic emergency.

UrgentBrooklynella hostilis (clownfish disease)

A rapidly progressing skin ciliate that preferentially attacks clownfish (Amphiprion spp.) but can infect other marine fish. Causes excessive mucus, sloughing skin, rapid breathing, and fast deterioration. Often fatal within 24–48 hours without treatment. Can be confused with marine velvet but has a distinct slimy, sloughing appearance.

UrgentAmmonia or nitrite toxicity

Gasping, gill damage, and lethargy caused by elevated ammonia (NH3) or nitrite (NO2) most common in new tanks, after filter failures, or following sudden bioload increases.

High priorityNew tank syndrome (uncycled tank)

Recurring or persistent fish illness in a tank less than 6–8 weeks old, almost always caused by the absence of an established nitrogen cycle. Beneficial bacteria that convert ammonia to nitrite and then to nitrate have not yet colonized the filter. Fish suffer from toxic ammonia and nitrite spikes.