Balancing the chemistry in your aquarium is crucial to long term success, especially if you house corals. That said, this balancing act doesn’t have to be complicated or significantly time consuming. For small aquaria, simply performing regular water changes with a quality salt will tackle most of the chemistry issues. For larger tanks, or those with a higher demand for reef building compounds, the answer includes basically dosing and testing. With routine testing, you can get a good snapshot of what your chemistry looks like. At that point in time, you can know calcium, pH, alkalinity, magnesium, and a whole slew of other things. Once you’ve established what your reef looks like chemically and how things trend naturally, then you can start adding the supplements to replace the essential compounds that are getting depleted as your corals grow. This supplementation can be done multiple ways (manual dosing or using reactors), and again the key is to regularly test to see how your reef responds. But testing only tells us one part of the picture. In addition to the testing, watch how the corals react. Sometimes they will thrive when the water has a particular alkalinity level, for example.
Again, none of this has to be complicated, but to recap, the best approach is to test frequently, perform regular water changes, does as needed, and monitor how your tank’s inhabitants respond. If you make changes, or feel that you need to, do so sparingly and make any transitions slow and steady.