ok nitrite is the second step of the nitrogen cycle. it is very bad for your fish. much worse than ammonia. water changes are a big part and with fish keeping the term "what if" could be very costly in the end. check your tap water before you put it in the tank. find out any threats it may cause to your fish but more important the threats it could cause to your beneficial bacteria. read this for sure. it will help you better understand the cycle process.
http://www.monsterfishkeepers.com/forums/showthread.php?t=224559
that is for fishless cycling only difference is your "pure ammonia" is fish waste. the only chemical additive i would recommend is prime. best stuff out there and it doesn't affect your cycle process but it converts ammonia to a non toxic form and detoxifies nitrite in emergencys. it is your water conditioner and everything all in one. i use it faithfully in more than 10 tanks. but to sum it up ammonia converts to nitrite, nitrite converts to nitrate. nitrate is your good stuff. but you do frequent water changes to keep the nitrate down. tank is cycled when tests read ammonia 0 nitrite 0 nitrate in between 5 and 15 but add fish slowly. also when you cycle with small fish the bio load of the large fish when introduced is way more. the large ammonia rush all at once can break down your cycle process and cause it to spike and can kill your fish. tap water from a city supply almost always has chlorine in it. this will also kill your beneficial bacteria. prime is also a dechlorinater. please read the link and ask all the questions you would like. these people are all wonderful and a great help. you have come to the right place!