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Figure Zone 4: A graph showing how to correct values within zone 4 by adding an alkalinity additive, such as baking soda (the blue arrow). |
Magnesium: Magnesium is LOW and you may need to increase it to about 1300 ppm. For more information consult this article.
Calcium and Alkalinity: Zone 4
Zone 4 problems are also a little harder to correct. It is typically caused by overdosing calcium RELATIVE to alkalinity, but does not necessarily imply that alkalinity is either to high or too low (though it is almost always too low). To correct problems in this zone, monitoring of calcium and alkalinity values during correction is especially important.
If this problem is extreme (i.e., you are far from the line at the left hand edge of zone 4), then water changes may be the best way to correct to the problem. In most cases, however, water changes aren’t necessary.
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Figure Zone 4: A graph showing how to correct values within zone 4 by adding an alkalinity additive, such as baking soda (the blue arrow). |
If alkalinity were less than 4 meq/L (11 dKH; the most common situation in zone 4; shown in Figure 5), I would advise correcting this problem by adding an alkalinity supplement until you have moved into the target zone (or zone 1). For systems with a pH of 8.2 or above, baking soda (sodium bicarbonate) is a good choice. For systems with a pH below 8.2, washing soda (sodium carbonate) is a good choice (though use some baking soda too if the correction is a large one and the pH gets too high; that is, above pH 8.5 or so).
