Velvet question

[indeco]

Recently I heard a reefer sharing his story on how velvet crushed his tank but after hearing it a question pop up in my mind.

Here the story go...

The reefer brought 4 new fishes (Blue Tang, Purple Tang, Powder blue tang, trigger) and was doing his due diligence to quarantine them for a month. During these period all fishes are eating well and no diseases or illness are spotted. He did not do any medical treatment during this QT period.

After QT period, he started introducing the fishes into the tank and soon he realised that the powder blue tang started to show sign of ich like symptom.

Unfortunately he did not react in time and by the time he knew it is not ich, it just too late.

So, is the powder blue tang having velvet but due to strong immunity system it did not react during the QT period? Or the velvet exist in the main tank and when the powder blue is introduced in, it got affected.

It is possible for fishes to resist velvet? My understanding is only few fish with very thick mucus will be able to handle it.

 

[Big G]

Without specific details, it is hard to explain this event with any accuracy. But what has been happening is that many wholesalers and shippers have been holding fish at "sub-therapeutic" levels of copper to suppress diseases like velvet. So depending on the fish, its immune system, etc., the fish finally get out to one of us. So the parasites that have be subdued recover and reproduce, so it appears as if these parasites have come from nowhere, suddenly. Where were they? Often the parasites have been deep in the fish's gills protected a bit from the sub therapeutic copper by the fish's mucous coating on the gills. Sometimes the fish will succumb to velvet without ever displaying the tell tale "velvet dusting" on the fish's skin. The velvet parasites often doing so much damage hidden from view with the gills. So it is very important to look for the "other" signs of velvet: lethargy, hiding from light, swimming into flow like a powerhead, gasping for breath, refusing to eat.

 

[indeco]

This assumption sound valid, if we are using this as the base then what will be a good period to quarantine the fish in order to be able to catch this relapse?