I'm doing a cycle on my tank at the mo! Into the second week and the nitrite is sky high (as it should be). I'm doing a 20-30% water change ev other day! my amonia is at 0%, my nitrate reads 30 units which is fine and my PH is dead 7. However on the second day when its time to change my water my nitrite reads aprox 1.4!! DANGER!!
I'm doing an intesive cycle with 5 amano shrimp, 1 mountain shrimp, 4 black widow tetra, 3 corys and 2 dwarf fire gourami I have slowly introduced. Not always a wise Idea but if you can control it and use hardy fish, lots of substrait cleaners and plenty of real plants it always seems to do well for me! You gotta make sure you note down your water test results before and after the water changes so you dont fluctuate your water 2 much!
I you look at a cycle chart amonia peeks in 7 days then nitrite peaks at 30 days and then drops right down.
If ppl say they managed to cycle their tank in a week they are either just short of genius or its just the calm before the nitrite storm and they just dont realise this.
A UV filter is helpfull (but expensive) as well because it kills disease before it can attack your fish in this delicate stage!
Remeber this is just my personal account and although it seems to work for me no two tanks are the same!!