tank is 6 weeks old, been having nitrite levels of 3 with strips. Api master test kit came today. Been doing partial water changes every 3 days. Today tested amonia 0, ph 7.6, nitrite 2, nitrate 0. 36 gallon bowfront live plants, manzanita wood, rocks. Have 6 harlequin rasboras, 6 neon tetras...