Replace 2-part additive with water changes?

[ItsMee]

If the tank is within the ranges of "Fish-only with live rock", "New tank, few corals", or maybe even "low demand", heck, might as well throw in "Mixed tank" as well under the chart titled "Suggested starting daily doses of this supplement in different aquaria" - is there an amount of water that can be changed through water changes that will keep these values in check rather than dosing? If so, how would you go about calculating it? Also, if for some reason someone was on a strict dosing schedule that was working perfectly and then they had to do an unscheduled, large water change, would this affect the balance of their dosing schedule in any way?

The chart I reference above can be found at "An Improved Do-it-Yourself Two-Part Calcium and Alkalinity Supplement System":
http://reefkeeping.com/issues/2006-02/rhf/index.php#1

[Randy Holmes-Farley]

It is unlikely you can maintain alkalinity demand this way unless there is essentially no demand or do huge daily changes. I show that here:

http://reefkeeping.com/issues/2005-10/rhf/index.php#8

for example:

Figure 23. Alkalinity as a function of time when performing very large daily water changes of 0% (no changes), 5%, 10%, 15% and 30% of the total volume EACH DAY. In this example, alkalinity is present at 4 meq/L (11 dKH) at the start and is depleted at a low rate of 0.2 meq/L per day.
http://reefkeeping.com/issues/2005-10/rhf/images/Figure23sm.GIF


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