I am getting wildly differing results measuring nitrites (NO3) in my 20 gallon reef cycling tank (now 3 weeks in). API says 5.0 Salifert says 0.1. Ammonia going to "0" overnight for 3 nights. Boost back to 1-2. This am boosted to 2.0 and dropped to 1.0 seven hours later. Suspect I am getting close to the end of cycling, but this API vs Salifert delta bothers me. Who to believe?