Well be that as it may, that still does not explain why baking soda is a non-lasting pH raiser (I've used it many times in the past, I know), whereas the Alkaline buffer certainly appears to stabilize and maintain pH.
Seachem says it's usage doesn't raise potassium or phosphate levels, and that it is a "sodium bicarbonate based buffer". Those statements do not reflect or deal specifically with what other elements may be in the formula to make it an effective buffering agent, perhaps justifying it's value and therefore extra cost over a grocery store bought baking soda product.
NaHCO3 (baking soda) is
a long lasting KH buffer in my experience using it so I guess never say 'never' and it doesn't last for you so never say 'always'.
Currently maintaining 840 gallons of 100% RO product water systems with GLA GH booster and NaHCO3 used to set the mineral content. CO2 injected high light to Walstad method tanks that go 3 months or more without adjustment or water change.
In answer to the question: "Does Seachem Alkaline Buffer contain anything besides sodium bicarbonate (plain baking soda) ? " , put to the Seachem lab,
"Besides sodium bicarbonate, Alkaline Buffer contains, sodium, potassium, magnesium, and other bicarbonate salts".
(These 'other bicarbonate salts' are not specified by Seachem).
So based on this reply it's NaHCO3 and;
1st - sodium, so more salt beyond the content of the sodium bicarbonate.
2nd - potassium which depending on the type might be Potassium Bicarbonate KHCO3 which happens to be the second elemental compound that has good solubility as an applied buffer.
3rd listed is magnesium which has ZERO bearing on carbonate buffer levels and,,, "other bicarbonate salts" which would be what exactly?
Water chemistry only recognizes a handful of elemental compounds that have effect on pH most of which have extremely poor solubility and or also effect GH.
NaHCO3 (baking soda), Sodium Bicarbonate which cost pennies and KHCO3 Potassium Bicarbonate which is 3-4x the price both mix extremely well but nothing else I've found does.
My lovely daughter has a Masters Degree in Chemical Engineering and works on the Everglades Restoration Project currently, we have had grand conversations on this topic.