I think my tank has finally cycled....hallelujah ! BUT...the API master kit was difficult to decode. I have a 75 gallon tank. Every time I tested the water the levels appeared to be zero. After 2 months of confusion, I took a different approach. I tested nitrates in the aquarium and in some "purified" baby water. At first glance, they looked identical. Thankfully I read someone's post about looking at the tubes from below. WOW, what a difference! I could clearly see my tank is at about 10 for nitrates. Has anyone heard of this happening? Anyway, if anyone is having trouble with their readings, try looking at the tubes from below instead of "head-on".