You should wait until the water complete cycled, then add a few
hardy fishes such as clown fishes, but get the cheap one then
wait for a week, keep testing the water, one question is mind
WHY WOULD YOU WANT TO DO THE WATER CHANGE WHILE IT
IS IN GOOD CONDITION?. Keep the hadry fish in the tank for
a week or two then doing about 20% water changes.
If you do water change before the tank complete cycle then you
would get rid of the good bacteria. I would wait.
Don't forget to get the skimmer after your first water change.
Good luck