fish

Ich (White Spot Disease)

The most common fish disease — caused by Ichthyophthirius multifiliis, appearing as small white spots like salt grains. Highly contagious but treatable with temperature increase and medication.

Symptoms

Small white spots like grains of salt scattered over body, fins, and gills (E1).
Fish scratch against decor, clamp fins, and breathe rapidly.
Spots multiply as the parasite completes its life cycle in the water.

Common Causes

Caused by Ichthyophthirius multifiliis (E1); marine white spot is a separate parasite (Cryptocaryon).
Introduced with new fish or contaminated water without quarantine.
Stress and temperature swings weaken resistance and speed the cycle.

What to Check

Check all fish for salt-grain spots — treat the whole tank, not only spotted fish.
Confirm freshwater vs marine system — the parasites differ and need different medication.
Stabilize temperature and improve water quality to support recovery.

What Not to Do

Do not treat saltwater ich with freshwater ich medication — the organisms are different.
Do not rely on temperature increase alone; sources differ on heat-only protocols — if pairing heat with medication, follow product guidance closely and monitor oxygen.

This guide is informational and does not replace professional veterinary advice. If fish are severely ill, consult a veterinarian.

Ich (White Spot Disease)

Symptoms

Common Causes

What to Check

What Not to Do

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Ich (White Spot Disease)

Symptoms

Common Causes

What to Check

What Not to Do