"CP" wrote in
:

Does anyone really know:
Can Ich survive in an aquarium with no fish, no living animals?

Ich can survive as a free swimming swarmer cell for about 48 hours. If
it does not find a host in that time period it will die. Ich can
survive as a multiplying mother cell in the substrate (or wherever it
lands) for approximately the same amount of time (depending on a few
variables including temperature and how engorged the mother cell was
before it left the host).

Ich medications are only effective against the free swimming swarmer
cell, not the infected Ich cyst or the mother cell stage.

If your tank is absent of fish for 4 to 7 days you can consider it Ich
free.

Ich is a relatively weak parasite and it is often the case that many
fish spend much of the lifetime hosting a latent Ich infestation.
Loaches, especially wild caught ones, are notorious for this.

A healthy fish can resist a mild Ich infestation to the point of
manifesting no visible symptoms. If the fish is subjected to stress
(e.g. due to transport or inappropriate tank or water conditions) the
immune system can fail and Ich can break-out manifesting itself as the
obvious and common white-spot disease. When a break-out occurs there
will be so many swarmer cells appearing in a very concentrated
environment that even a healthy fish will often not be able to fight off
the parasitic assault effectively.

Chances are the fish you are buying are hosting a latent infection
before they ever enter your tank. I would suggest you check your water
conditions before adding new fish and consider finding a new supplier or
at the very least quarantine your new fish and treat them for three days
with QuickCure before introducing them to your aquarium.

Some decent referenced Web info on the life cycle of Ichthyophthirius
multifiliis:

http://parasitology.informatik.uni-u.../n/h/0702.html