Your aim with a fish-in cycle is to keep both ammonia and nitrite from ever getting above 0.25ppm.
Don't forget that the fish are producing ammonia all the time, so if you test the water and it's at that 0.25ppm level, then you'll need to do a water change then, rather than leaving it to go up even higher.
If your ammonia and nitrite are at zero, then you don't need to do a water change.
Don't forget that the fish are producing ammonia all the time, so if you test the water and it's at that 0.25ppm level, then you'll need to do a water change then, rather than leaving it to go up even higher.
If your ammonia and nitrite are at zero, then you don't need to do a water change.