lol
It is both exactly theoretically and experimentally accurate to say that bicarbonate dosing lowers pH a small amount when first dosed.
I've tried it, and published the results long ago, and anyone challenging me should simply try it themselves.
Everyone has baking soda in their home. It should not take more than 2 minutes to try if you have a pH meter.
Randy answers many questions in this complex relationship.
reefs.com
From it:
Alkalinity Supplements
One of the most common issues that reefkeepers face involves supplementing alkalinity while maintaining a reasonable pH. Alkalinity supplements impact pH in a variety of ways. One of these ways is the immediate altering of the pH. Different alkalinity supplements have different immediate impacts on pH, as most reefkeepers are aware. This impact is why, for example, limewater needs to be added slowly to a tank but sodium bicarbonate does not.
For this discussion, let’s presume that we want to supplement the carbonate alkalinity of a reef tank. That is, in the end we want to increase the bicarbonate and carbonate levels in the tank. There are a variety of ways to achieve this end, and these different ways have different immediate impacts on pH. Three of these ways (and combinations thereof) are fairly common in reefkeeping. These ways are addition of bicarbonate, carbonate, and hydroxide. In a reef tank that is permitted to equilibrate its total CO2 levels with the atmosphere, these additions all end up with the same final pH. That is, it is only the amount of alkalinity added that determines the final pH, not the nature of the additive itself.
In the short term, however, the impact on pH is very different. To quantify this, I measured to pH change on adding 0.5 meq/L of each of these
alkalinity supplements to freshly made salt water (Instant Ocean made to S=35; alkalinity measured to be 2.26 meq/L by titration). Here’s the result for the pH found immediately, and then after 24 and 120 hours of sitting, unstirred, in an open 500- mL beaker:
| Supplement | Initial pH | 24 hour pH | 120 hour pH |
|---|
| none | 8.10 | 8.11 | 8.21 |
| 0.5 meq/L HCO3- | 8.06 | 8.15 | 8.33 |
| 0.5 meq/L CO3– | 8.44 | 8.28 | 8.34 |
| 0.5 meq/L OH- | 8.76 | 8.47 | 8.33 |
| 0.5 meq/L H+ | 6.91 | 7.91 | 8.15 |
From this data it is clear to see the large increase in pH caused by the addition of hydroxide, and also the significant increase when using carbonate. Bicarbonate, on the other hand, shows the expected slight decrease in pH, but not nearly as much as is found with a strong acid of equal concentration. It is also clear that after sufficient time to equilibrate with atmospheric CO2, these differences disappear, and the pH is the same for all of the 0.5-meq/L alkalinity additions. This is an important result:
in seawater in equilibrium with the atmosphere, for a given alkalinity there is a single pH that results, regardless of what was added to get to that alkalinity.
Here’s how to think of these additions. When these chemicals are added to the water, there is a change in the relative concentrations of carbonate and bicarbonate, and it is the ratio of these two ions that determines the pH.
