[unclejed]

Hello Vu.There are some who would tell you that once "the numbers" are all good the cycle is over and you are ready to go, I am not one of those. What many beginner (even some advanced) aquarium keepers are not (fully) aware of is that the full cycle takes at least 6-8 months. The reason being, mainly, is this is the time required to fully cultivate a total beneficial bacterial base and achieve a saturation of such. Also, allowing the tank to "season" and go through the inevitable mini-cycles and diatom blooms and get fully established is the key to a healthy and stable tank in the future. You could have one fish after about the 6 week mark, let the tank get established by light feeding and going through a moderate light cycle (6-8 hours) for the next 3 weeks. After that, add a few clean up critters (crabs and/or snails) and allow the tank to "catch up" to the added load (you may at this time add some live bacteria to help in this process) and give it another 2 weeks doing all your tests on a regular (weekly) basis and determine if the tank is stable. Water changes of 30% should be carried out once a month to once every 5-6 weeks. Coral should not be introduced (even soft) until the tank is around 3-4 months old. Too many beginners don't exercise the proper patience and discipline at this early stage of getting their tank going only to have problems and head aches down the road. Once the tank has gone through this full cycle period and the tank is stable, then and only then, should you add more difficult coral like hard coral. I always employed a bit of advice I got when I was starting out to add bacteria after each water change for the first and subsequent next 4-5 changes. After the 4th water change then and only then add to the tank and minimally at that.
Another good tactic I learned is to add (whatever you are adding) a couple days after a water change. This gives the new creature fresh minerals and trace elements and a good 3-4 weeks (I adhere to 4-5 week intervals between changes) to adjust to the new water parameters, light, temp etc. before disrupting the tank for the next water change.
I hope this helps.