Even when using media to seed a tank or bottled bacteria for a fishless cycle, if ammonia is dropping, nitrites should be tested. In order to assess where in a cycle things stand, we need to know more information than you have provide. I would need to know how much ammonia you add and when and then all reading taken for ammonia and nitrite. With this info it becomes a lot easier to know exactly where things should be vs where they are and why.
Using an API (or similar) test kit, the number you do not want to exceed is 16 ppm of nitrite and I prefer to use 15 ppm as the line to be safe.
The fastest way to cycle is not to do any water changes without cause.
The danger of too much nitrate, and the cycle itself, is that it can result in dropping pH due to one's having the carbonates in the tank used up. Carbonates are a key component of KH which is what holds pH steady. Use up the KH and the pH falls and when it get into the 6.5 range or below, a cycle will stall.
Finally, there is no need to do 9:1 testing. It is overkill and usually more subject to inaccuracies. There is a good step by step set of instructions for how to do diluted testing that is easy and accurate here
http
/www.fishforums.net/index.php?/topic/433778-rescuing-a-fish-in-cycle-gone-wild-part-il/ These instructions are there for determining how much salt to add to help during a fish in cycle. However, the diluted testing process is the same for any form of diluted testing for nitrogen compounds.
One last note, knowing how much ammonia has gone in will let us determine what the maximum possible nitrite should result from that. In the cycling article here the ammonia ammounts and timing of their being added is intentionally designed to make it impossible for one to have too high nitrite even when it hits the top of the test scale we know it should be OK. It is when folks depart from the directions and add too much or too soon that the nitrite can go nuts.
In order to know if you need to do a water change I would want to know what your tap pH and KH are and then what they are now in your tank. Assuming your nitrite is actually under 16 ppm and your pH is not dropping rapidly (and HK too), there is no reason to change any water. While the nitrate may be high, if it is not slowing the cycle, there is no need to change the water. If your nitrite is under 16 ppm, then changing water will reduce that which, in turn, will slow your cycle. If your nitrite is 16 or more, no matter what the nitrate level is, you must do about a 1/3 or so water change. The goal is to drop it to about 10 ppm. This leaves a good amount to keep the nitrite bacs reproducing and gives you 5 or so ppms headroom for it to be able to rise again safely.
