Recipe #1 is for use in reef aquaria whose pH is normal to low. In practice, more reef aquarists end up choosing this recipe than Recipe #2. It will tend to raise pH due to its alkalinity part's elevated pH, as do most of the commercial two-part additives. The increase in pH depends on the aquarium's alkalinity and, of course, on how much is added. Adding on the order of 0.5 meq/L of alkalinity increases the pH by about 0.3 pH units immediately upon its addition (and even higher, locally, before it has a chance to mix throughout the aquarium).
If you are using limewater (kalkwasser) and the aquarium is at pH 8.4 or above, this recipe is not the best choice. Otherwise, it is likely to be a good option. It is twice as concentrated as Recipe #2, because the baking process makes the baking soda more soluble.
Recipe #2 is for use in reef aquaria whose pH is on the high side (above 8.3 or so). It will have a very small pH lowering effect when initially added. The pH drop achieved will depend on the aquarium's alkalinity and, of course, on how much is added. Adding on the order of 0.5 meq/L of alkalinity drops the pH by about 0.04 pH units immediately upon its addition.
f you are using limewater (kalkwasser) and the aquarium is at pH 8.4 or above, this recipe may be the best choice. It is half as concentrated as Recipe #1 because the raw baking soda is less soluble because it's unbaked
Recipe #1
Introduction
This two-part additive system is similar to the many commercial two-part additive systems. It allows aquarists to supplement calcium and alkalinity without greatly skewing the water's ionic balance (something that is claimed by many of the commercial products, but that is not independently verified). Equal addition of the two parts to a reef aquarium will provide calcium and alkalinity in approximately the same ratio used in calcification by corals and coralline algae.
One part is calcium chloride dissolved in water, and the other part is baking soda (either baked or not prior to use) dissolved in water. The balance between these two additives is very important, and the recipe is designed for aquarists to dose equal portions of the two parts every time they dose. An aquarium using such a balanced additive system is unlikely to undergo large short-term swings in calcium and alkalinity, as can happen if an aquarist using independent additives were to inadvertently overdose one or the other. This problem is surprisingly common, and using balanced calcium and alkalinity additive systems for most additions serves to eliminate that potential danger.
A "third" part of this additive system contains magnesium, sulfate, and chloride. It needs to be added only once in a while at a fixed rate relative to the other two parts. It cannot be readily combined with either of the other parts, based on the ingredients discussed here that are readily available to aquarists (commercial systems may have more chemicals to select from, such as sodium sulfate, allowing more flexibility). This third part is necessary to prevent magnesium depletion, and to prevent abnormal chloride and sulfate ratios in the aquarium.
The seven most abundant ions in seawater, in decreasing order of concentration, are chloride, sodium, sulfate, magnesium, calcium, potassium and bicarbonate. Using this new recipe will keep all of these ions in their appropriate ratios (detailed below).
Comparing the Two Primary Recipes
This article actually details two primary recipes. One uses raw baking soda, and the other uses baking soda that aquarists bake before use. The baking drives some of the carbon dioxide out of the baking soda, and raises its pH as well as its alkalinity. Be careful about substituting other brands for the Dowflake and the magnesium chloride sold by the Dead Sea Works company. A later section in this article details substitution issues.
Recipe #1 is for use in reef aquaria whose pH is normal to low. In practice, more reef aquarists end up choosing this recipe than Recipe #2. It will tend to raise pH due to its alkalinity part's elevated pH, as do most of the commercial two-part additives. The increase in pH depends on the aquarium's alkalinity and, of course, on how much is added. Adding on the order of 0.5 meq/L of alkalinity increases the pH by about 0.3 pH units immediately upon its addition (and even higher, locally, before it has a chance to mix throughout the aquarium).
If you are using limewater (kalkwasser) and the aquarium is at pH 8.4 or above, this recipe is not the best choice. Otherwise, it is likely to be a good option. It is twice as concentrated as Recipe #2, because the baking process makes the baking soda more soluble.
Recipe #2 is for use in reef aquaria whose pH is on the high side (above 8.3 or so). It will have a very small pH lowering effect when initially added. The pH drop achieved will depend on the aquarium's alkalinity and, of course, on how much is added. Adding on the order of 0.5 meq/L of alkalinity drops the pH by about 0.04 pH units immediately upon its addition.
If you are using limewater (kalkwasser) and the aquarium is at pH 8.4 or above, this recipe may be the best choice. It is half as concentrated as Recipe #1 because the raw baking soda is less soluble because it's unbaked.
Recipe #1
Recipe #1, Part 2: The Alkalinity Part
Spread baking soda (594 grams or about 2 ¼ cups) on a baking tray and heat in an ordinary oven at 300°F for one hour to drive off water and carbon dioxide. Overheating is not a problem, either with higher temperatures or longer times. Dissolve the residual solid in enough water to make 1 gallon total. This dissolution may require a fair amount of mixing. Warming it speeds dissolution. This solution will contain about 1,900 meq/L of alkalinity (5,300 dKH). I prefer to use baked baking soda rather than washing soda in this recipe as baking soda from a grocery store is always food grade, while washing soda may not have the same purity requirements. Arm & Hammer brand is a fine choice. Be sure to NOT use baking powder. Baking powder is a different material that often has phosphate as a main ingredient
