so velvet which i thought was ich destroyed my tank in a matter of 5 days. i went fallow for 6 weeks, added 3 healthy tangs and a wrasse last week and they are doing great now. It said the life cycle of the velvet is different than ich, 5 weeks is normal for the tank to be clean 99% success if you wait 8 weeks. Cut and pasted the right up because it would be a link to another fish forums.
There is no such thing as a dormant stage for MV. The parasite can�t wait around for another host. It MUST go through its cycle, or die. It doesn't 'wait' for better times. It was recorded that a cyst can exist for up to 5 weeks before releasing its free-swimming dinospores. This is rare but possible.
Like MI, the display aquarium, if infected has to be treated. Let aquarium go fishless (without any water additions, contamination from infected tanks, live rock additions, etc.) for at least 8 weeks and the tank will be free of MV. This 'fallow period' has over a 99.99% chance of success.