I have a QT with LR in it if medication is needed then I isolate in a separate hospital tank. QT is for isolation and observation before they go into the DT not medicating fish. Medicating fish a whole different world you can set up a hospital tank in about 10 mins . I have a 5g tank for treating fish and a 10g tank. run a air line and water you have to do water changes every day but they are not that huge.

I make my QT so there is hiding spots that are near normal for the fish they don't get as stressed out before they go into the DT. the only fish I lost in the past 6 months was a blond Naso tang from a power outage in the night. only 1 fish out of three tanks I would say that is a good ending considering the power was out for 8 and half hours. I guess I could have fired up the generator but didn't want to wake up the neighbors

Bill.
Bill

Oh, I read this part:

...and thought you were treating fish with Ich from your display. Either way, quarantine before introduction or quarantine for treatment...the same steps apply. If you're worried about contaminating the quarantine tank with Ich because you recently had Ich in your display then use the Prime as I described above.

if they were infected with ich, might want to check up on it's life-cycle, as doubt it's really gone. QT is still a good idea for new fish as there's more than ich out there, but don't be surprised when you take your new fish out of QT and introduced into the display you see signs of ich again.

For Ick I use garlic extract and selcon soaked food. You can look at Ick like shingles and a person it is caused by stress and is a nervice system disease. the garlic and selcon boosts their ammune system and then they can fight it off with ease. I have not seen Ick in my DT for over a year and a half.

Bill

to answer your question about medications killing the bacteria in your rocks/filter - the answer is only if you use medications that kill gram negative bacteria. The nitrobacter and nitrosoma bacteria families are all gram negative, so broad spectrum anti-biotics that are lethal to both (like tetracycline) can shut down a bacterial filter. Erythromycin is only toxic to some gram negative bacteria and is specifically targeted to gram positive bacteria, so it can be dosed with a measured sense of security that it won't reset your bacterial filter to zero, though it might cause some instability.

I'm not aware of any common ich treatments that fry beds of nitrosoma and nitrobacter bacteria, though some of the more noxious ones might just kill everything except the fish. I don't think most copper treatments affect the bacteria bed either.