How long will a filter stay cycled?

Unless this is just after a water change my guess is there is likely enough left over food and fish waste to make ammonia at some level for a few days. Unless it is really dirty though far short of a week. And the size of the bacteria colony will start to go down almost right away, so the bioload will have to be added carefully.
 
I have ammonia, I'll add a few drops for a couple days till I get to the fish store again.
 
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