Join Date: Oct 2007
Location: Ontario, Canada
Ich parasites cannot spontaneously appear in a closed environment like an aquarium.
They have to be introduced by something, say new fish, plants, decor, etc.
Ich "spontaneously" and persistently appearing in aquariums is a myth. If they seem to be appearing and disappearing in cycles, it is only because the ich on the fish have left the host to repeat its life cycle, then coming back several days/weeks later appearing as if they were new parasites.
They have to introduced from some sort of external source first.