Ich / White Spot

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

• Pale dots, rubbing or breathing changes can occur. Gill-only infection may produce no visible dots.

Possible causes and look-alikes

• Freshwater ich is Ichthyophthirius multifiliis; marine ich is Cryptocaryon irritans. Other skin and gill organisms may look similar.

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.
• Suspected ich warrants urgent fish-health assessment; confirmed infection needs prompt, system-specific treatment. Do not wait for breathing distress or deaths.
• Check oxygen and water promptly, avoid transferring wet equipment between systems, and seek parasite identification.

Treatment and correction context

• Management must account for susceptible life stages and the affected system, not just visible fish. Disappearing spots do not prove clearance.
• Do not apply one heat or medication protocol across freshwater, marine fish and reef inhabitants. Copper does not kill every ich life stage, and suitability depends on the animals and system.

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.

• UF/IFAS: Freshwater White Spot Infections

  Freshwater ich identification, life cycle and susceptible treatment stages.

• UF/IFAS: Marine White Spot Disease

  Cryptocaryon life cycle and marine-specific management limitations.

• UF/IFAS: Submission of Fish for Diagnostic Evaluation

  Case history and contacting a diagnostic service before collecting samples.