Dropsy

When to act urgently

Breathing distress, rapid deterioration, inability to remain upright, major wounds or multiple deaths require urgent aquatic-veterinary or fish-health help. Check aeration and water immediately; do not wait to match a photograph.

What you may notice

• Body swelling and lifted scales; breathing or buoyancy may also change.

Possible causes and look-alikes

• Kidney or gill dysfunction, infection, tumors and environmental problems are possibilities.

Check first

• Record species, aquarium type, recent arrivals or changes, appetite, breathing, and how many fish are affected. Check aggression, injuries, filtration and aeration.
• Test ammonia, nitrite, pH and temperature; measure dissolved oxygen where possible and salinity in marine/brackish systems. Correct verified environmental problems using suitably prepared water, avoiding abrupt chemistry changes.
• Record onset, recent diet, water results and other signs. Do not assume every swollen abdomen is dropsy.

Treatment and correction context

• Seek prompt veterinary assessment, especially with breathing or buoyancy changes.
• Salt and antibiotics cannot be assumed to resolve the underlying problem; treatment depends on diagnosis and species.

Record for your next step

Write down onset and progression, species, affected/total fish, recent introductions, feeding observations, dated water results with kit units, and every action or product already used. Contact the diagnostic service before collecting or shipping samples.

Sources and scope

Source checks: 2026-10-03. Educational editorial summary; no independent veterinary review.

• Fish Vet: Dropsy in Fish

  Fluid-balance signs, underlying organ problems and diagnostic limitations.

• UF/IFAS: Submission of Fish for Diagnostic Evaluation

  Case history and contacting a diagnostic service before collecting samples.