I suspect youre getting false test readings. If in doubt, take a water sample to an LFS that does NOT use API kits and see what readings they come up with.
The purpose of a cycle is to create bacteria that will be consuming ammonia and nitrite from your livestock, but you have to get the bacteria from somewhere initially. Why is it called a cycle? Because the tank will go through three phases: ammonia will rise and fall, then nitrite will rise and fall even quicker, and lastly nitrate will rise and fall. Once Ammonia should read 0 and Nitrate is less than 20ppm, the cycle is complete and livestock can gradually be introduced. The bacteria population will increase with the new bioload, processing waste and converting it to nitrate rapidly. However, it is important to note that overloading the aquarium with too many fish initially can exceed what the bacteria can handle. This is why it is best to add new fish slowly over the next few months. The bacterial levels will adapt if you don't overload the system with too many mouths to feed.
How long does the cycle generally last? Using the three test kits to measure results daily, you'll likely see the process takes 21 days. Test the aquarium daily for Ammonia, Nitrite and Nitrate, logging the information on paper or perhaps in a spreadsheet or app. The more data points you collect over time will graph the rise and fall of each of these parameters. No livestock of any kind should be placed in the aquarium as long as you have any measurable traces of ammonia or nitrite because these are toxic to fish and invertebrates. Start planning what you'll want to put in your aquarium while you have a few weeks to wait. There's no reason to rush this process. A good solid foundation will benefit your future reef and handle the bioload adequately.
Also - If you are running the system with a sump that has a refugium or Algae Turf Scrubber section, don't add any light or plants because the system is too clean.
