Depends on the water parameters. If there’s any ammonia or nitrites I’d recommend a water change ASAP but if the tank is fully cycled you could probably just do one every week or every two weeks. A standard water change is between 25-50% of the water.
I agree with Lilbub, really depends on your parameters. If it’s not cycled you’ll need to do waterchanges as needed, but if it is generally it’s every week. Although if your parameters are usually really good you might be able to stretch it to two.