[SubRosa]

Our fish live in the ocean."Ich" lives in the ocean.Yet most of the fish that come in show no signs of any external parasites and show no obvious symptoms.What causes the runaway outbreaks we experience in captive situations is environmental stress brought on by bad handling in holding and transit,bad water quality,poor diet,uncomfortable surroundings etc.That is why old established tanks often seem ich proof.Given good care and suitable surroundings fish are very resistant to disease.The fish are used to each other,and newcomers generally sink or swim without greatly affecting the more established residents.Unless the newcomers are real bad actors like Undulate Triggers or perhaps a Sohal or Clown Tang,in which case no tank is immune to the stress that can cause an outbreak.