I definitely agree that the fish my recover but whatever may still be in the tank but I try to go 3 weeks after I have moved new fish out before adding new ones to allow any fish disease to die if there no host it can’t live but I can see how this thinking is flawed with a bacteria but it has worked for me so far I do also keep a empty tank and some extra cycled sponge filters in my sump just in case I’ve released in this hobby it’s better to be prepared for as much as you can be