This fish went through about a week and a half of observation, noticed some ich so 30 days copper at max level. then about a week at about half dose to see if all was clear. Moved the following weekend. Fish didn't show signs until the move.
I did not qt before moving to my 125.
Not bad but could be a cyst that formed before u ramped up copper and that hatched while you were at half the dose. Statistically low probability though.
If I'm not going to observe for 2-3 weeks I prefer to keep fish for one more week at full strength and remove directly without allowing the infection. There are reports of cysts that can last longer especially at lower temperature. Not sure if they can withstand copper for 4 weeks though. It also could have been dormant disease in ur tank.
Maintaining an ich free tank is no easy task, I thrive more to prepare fish to handle it via fattening in qt or introduction tank, boosting foods with vitamins.
I had velvet years back in my tank which killed half of my fish, took fish 2-3 weeks to die as they were healthy (vs 48 typical kill time). I stayed months without any new fish intro then made sure to properly prepare my fish and I now have more than 90 fish in the system with no sign of ich or velvet.
Ich was there and I could see outbreaks although mild and no losses. With time I saw it less and less frequently till I never saw it again.
I added 4 Achilles in last 10 years all well QTd one for more than 6 months and non made it before. Last one made it perfectly and has been doing great for close to a year, hence I'm more for living with ich than trying to eliminate it.
One theory says that as fish immunity improves if ich isnt seen on any fish for 6 weeks then the disease has wiped itself, again all theory.
Believe the recent microbial check for tank water technique will allow us to understand more how things are going in our tanks and how diseases evolve.
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