Heath I am following along here because I had the same issue. Did you by chance start your tank with tap water? That is what I did when I first started ( that is what my LFS
said was the best) and boy was that a mistake. I started off with really high nitrates added a raw shrimp and thought all was going great when my ammonia spiked, then lowered...still had some nitrates though, then nitrite spiked and nitrates were at 0. Nitrites were still high and then all of a sudden my ammonia started appearing again after weeks of cycling. Now I am back to square 1. Been doing water changes with RO
water added a new shrimp and letting it do it's thing. Hopefully I am doing it right this time still not sure
...noob move on my part, but hey it's all about learning from your mistakes right?