Ok, more than likely, it is cycled. Me personally, I'd want to be sure, so I'd wait until I saw that it could process ammonia all the way through to nitrate before I put my fish in.
As long as the pH is the same (or very, very close) all new water will not shock them. I change almost all the water every single week in my tanks and my goldfish are extremely happy and healthy. Clean, fresh water is the very best way to keep your fish healthy, no matter what anyone tells you to the contrary. I wish that myth would die.
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