I dunno how the chemi pure and purigen pulled your nitrates down so fast... Ive had my tank up and running for about 5 weeks. Added shrimp 4 weeks ago had two mini cycles and my nitrates were super high , did a 40% water change brought them down some , but still around 60 -80 and I added chemi pure, rowa phos and pura complete and none of those did anything for my nitrates. They did help phosphates though. Also my ammonia and nitrites were at 0 before I added the chemicals.
Just be careful not to move to quickly. I still have a week or two of doing water changes before I get to add a fish. Its a long process. That makes for 6-7 weeks of cycling for me.