The myth that ich is present in all aquaria is just that, a myth. There is absoultely no scientific data anywhere to support the statement it does. It has the ability to infest at a low rate on a particuliarly resistive host (which would have to go unnoticed by the keeper), but cannot survive without hosts.
Dr Burgess (writer for PFK and co-author of
A to Z of Tropical Fish Diseases and Health Problems) dismisses the myth of ever present ich as "rubbish".
These are two of the better/best pages on Ich:
http
/www.cichlid-forum.com/articles/ich.php
http/www.skepticalaquarist.com/docs/health/ich.shtml
In research it was found that in cool ponds there were no traces of ich after about a week without hosts. This will be shorter in a tropical tank as the higher temperatures accelerate the life cycle (hence why people sugeest increasing temperature when ich infects a tank - though without another form of treatment this will just cause your fish to die quicker).
Tempest:
There are only three stages to the Ich cycle:
Trophont: where the pathogen is buried under the fishes skin and is feeding off the body fluid of the fish. this is the "white spot" that can be seen on a fish.
Tomont: is when the pathogen is encysting on the substrate or other surface and reproducing, leading to hundreds of
Thermonts: which are free swimming and must find a host before dieing.
Each cycle produces hundreds, if not thousands of thermonts per trophont. This is why ich cannot be in all aquaria all (or even most) of the time. Where are all the other thermonts going? Also, ich hgas no long term dormant stage where it can lie in wait for a fish to be unhappy.
