I suggest still taking a look at the aging barrel by wiping it with a paper towel from time to time , i was doing exactly like you before in fear of putting untreated water to the tank , i was putting prime 5 min before the wc transfer, and after a month my barrel was full of orange slime coat , like the gunk we found when cleaning canister filter, now i put prime in the tank and just add the untreated aged water.