ich, healthy fish, fallow tank question

[muda]

Please shed some light here.

If ich parasite can not survive in fallow tank, how it survives in that tank where all fish seems totally healthy ?

I have juvenile sixline in 300 gallon tank that I can not catch. She seems completely healthy for several months already. I had another wrasse along that showed no signs of infection too, but that one somehow took offered bait. So where ich is hiding ? Or it is not ?

 

[Dmorty217]

ich starts in the gills. If the fish have immunity to ich they still have ich but don't show signs of it thus allowing the lifecycle to continue

 

[muda]

Thanks.

 

[muda]

I came to some confusing thoughts after some thinking job.
If fish can be immune to ich and still carry parasite, so how can we be sure that we not introducing ich in to display after quarantine ? Observing fish this way is not enough. Fish can look completely healthy and then bah !!! we have ich in tank.