Sohal tang mysteries

[Motaz]

Quick question:
I have a shoal tang living in my quarantine facility, and it has been there for roughly 3 weeks now. All seems to be well with the fish; swimming around happily, eating well and generally in good condition.
Yet, a funny thing happens at night if you turn the lights on. It appears as though the fish has white spot (crypto), but when you look at the fish again in the morning...the fish is perfect again! I have noticed this on more than one occasion. I am scepticle about introducing the fish to my display tank, as I fear it might infect the other fish.
What could these white spots be, as the random occurrence of them at night makes me believe that it is not crypto.
Any ideas?

 

[sanchoy]

Well turn off the lights, then when you see the white spots turn on the lights to confirm. If its ick the fish will rub against some sort of surface area.

 

[scuzy]

are you medicating in the QT? I vote to proactive treat for ich than to monitor for ich thinking it doesn't have it.