Using the bottled bacteria is probably how you're already seeing nitrite and nitrate, but even with these products the colonies have to establish in your media/ substrate, etc. and stabilize. It's been a few years but I think it still took a month or 6 weeks for my tank to be balanced with dr tims and a half dozen baby giant danios in a 90 gallon tank. Without the bottled stuff it could have been 3 months. I personally would probably do 50% every other day until ammonia drops to 0, but I would also test an hour or so after a water change to see what impact your wc has. As mentioned above, you have to decide for yourself what is acceptable. The reason we test for ammonia, nitrite, and nitrate is they are all toxic to fish, As the colony stabilizes and your ammonia gets to 0, then your nitrite will get lower and lower until its stable at 0, and everything is being converted into nitrate then your tank is cycled. But depending on tank size and what fish you put in, you may be able to decrease water changes to twice a week, or once a week, testing will tell, you'll still need to do wc to reduce nitrates. And when you add other fish you may be back to frequent water changes while the colony balances again to the new bioload.
