depends on what fish it is... most the fish I get that are juvies go into my community tank. and tbh w/ the big guys I don't have another big pool/tank laying around so they go directly in. BUt I also don't QT fish ect for sickness just aggression related things... so when something gets sick the whole tank gets treated anyways. exception to that is feeders. QT 7 days min or more if they are unhealthy. I have taken the chance /w batches and immediately added them but its pretty rare.