Freshwater Tropical · Goldfish
Freshwater Ich (White Spot Disease)
The most common freshwater fish disease. Tiny white spots resembling grains of salt cover the body and fins.
Severity: Moderate
*Ichthyophthirius multifiliis* is the most familiar freshwater parasite. The trophont stage embedded under the skin appears as white salt-grain spots; once it drops off and divides as a tomont, the released theronts re-infect the host. Only the free-swimming stage is vulnerable to treatment — which is why temperature-driven life-cycle acceleration matters.
Causes
Almost always introduced via new fish. Stress and low temperature reactivate latent infections. Common in pet-store stock that has been bagged repeatedly.
Treatment
Raise temperature gradually to 28–30 °C (82–86 °F) to speed up the life cycle. Treat with **Forma-Green** or malachite-green + formalin for 10–14 days. Continue 5 days after the last visible spot disappears — invisible tomonts are still cycling.
Recommended medications
Antifungal
Forma-Green
Formaldehyde + malachite green combination — broad-spectrum treatment for ich, costia, trichodina, oodinium, and fungal infections.
from $24.00
Recommended equipment
Hardware that prevents, monitors, or treats this condition — listed with the most important first.
Prevention
Quarantine new fish for 2–3 weeks. Maintain temperature stability. Avoid chilling stress during water changes.
Frequently asked questions
Why did the spots come back after treatment?
You stopped treating too early. The visible spots are only one life stage. Treat for at least 5 days past the last visible spot to break the cycle completely.