"Prevention is always preferable to treating "Ich" (or any disease) after an outbreak is in progress. Preventing introduction of this parasite is one of the most important reasons all incoming fish should be quarantined. Transport and handling can cause newly arrived fish who may be asymptomatic carriers (those with no obvious clinical signs) to break with active disease, serving as a source of infection for other fish they may come in contact with. At the warm water temperatures required for many aquarium fish, active disease will often become evident 1–3 weeks after shipping. For this reason, a minimum 30-day quarantine period is recommended for new fish."
CIR920/FA006: Ichthyophthirius multifiliis (White Spot) Infections in Fish
CIR920/FA006: Ichthyophthirius multifiliis (White Spot) Infections in Fish