Wasting Disease / Fish TB

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

• Chronic weight loss, poor condition or skin lesions may occur.

Possible causes and look-alikes

• Inadequate intake, other infections and internal disease can cause wasting. Weight loss does not diagnose mycobacteriosis.

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.
• Review nutrition and feeding access. Use protective gloves, cover cuts and keep aquarium water away from wounds.

Treatment and correction context

• Seek laboratory-supported veterinary assessment rather than labeling every wasting fish contagious or prescribing indiscriminate antibiotics.
• Some fish mycobacteria can infect people. Persistent skin lesions after exposure warrant medical advice that mentions aquarium contact.

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.

• Iowa State CFSPH: Piscine Mycobacteriosis

  Mycobacteriosis diagnosis, exposure protection and human infection risk.

• UF/IFAS: Submission of Fish for Diagnostic Evaluation

  Case history and contacting a diagnostic service before collecting samples.