Ich
Cryptocaryon irritans (saltwater) / Ichthyophthirius multifiliis (freshwater)What does Ich mean?
Ich is the common name for two related parasitic protozoans that cause white spots resembling salt grains on fish. Saltwater ich is Cryptocaryon irritans; freshwater ich is Ichthyophthirius multifiliis. Both have free-swimming and cyst phases; treatment must target the free-swimming phase.
How is Ich used in aquariums?
Saltwater treatment options: copper-based (Cupramine, Coppersafe) at 0.35-0.5 ppm for 30 days minimum, or chloroquine phosphate at 60 mg/gallon. Freshwater: heat (raise temp to 86°F for 14 days, only for fish that tolerate it), formalin/malachite green, or Ich-X. Always treat in quarantine, never the display tank with corals or invertebrates.
How Ich fits the bigger picture
Understanding Ich matters because it's connected to broader husbandry decisions: disease prevention is cheaper than treatment - quarantine + dipping protocols paid back the first time you avoid a tank-wide outbreak.
Browse the Fast Aquatics care library for full husbandry tutorials covering Ich in context.
Frequently asked questions
What does Ich mean in fishkeeping?
Ich is the common name for two related parasitic protozoans that cause white spots resembling salt grains on fish. Saltwater ich is Cryptocaryon irritans; freshwater ich is Ichthyophthirius multifiliis. Both have free-swimming and cyst phases; treatment must target the free-swimming phase. Saltwater treatment options: copper-based (Cupramine, Coppersafe) at 0.35-0.5 ppm for 30 days minimum, or chloroquine phosphate at 60 mg/gallon.