You are correct Josh. Ammonia should be 0, nitrite should be 0, and nitrates low before adding livestock. Nitrate build-up is a normal part of the biological processes within the filter and can be removed with plants and water changes. If you can obtain a perfect balance then you could theoretically go without doing a water change ever again. Although you would need a calcium reactor to add your trace elements back into the water used by the corals and fish metabolisms.