Lake Tanganyika Species • What is your water recipe

[Ptyochromis]

Good question!

Because the main source of buffering capacity for a home aquarium is bicarbonate. It's cheap, easy, reliable, and has the appropriate dissociation equilibrium to maintain pH where we want it.

Baking soda- NaHCO3 - sodium bicarbonate - alone will stabilize pH at 8.2
Soda ash- Na2CO3 - sodium carbonate - in combination with NaHCO3, pH can stabilize at 9.2

These are the main components of commercial rift lake buffers. There are other buffer systems that can be used, but they will have a larger effect on the nutrient balance. For example, a phosphate buffer will add phosphate to your tank...

Why not use MgSO4 (Epsom salt)? It will add hardness without adding carbonates

[triscuit]

... and will not affect pH or buffering capacity. MgSO4 only affects hardness.

[triscuit]

Why would anyone want a pH of 9.2 when even the lake is only 8.66-9.06?
As I understand it lake pH is rising and the fish still struggling to adapt to this.
pH 8.2 more than high enough?
(Esp as most tank pollutants (nitrogen compounds) become more toxic with increased pH and filtration bacteria ever less efficient at above 8.2 -8.6 ish)

Ask SeaChem. They're the ones selling that mix.

If you are shooting for the average annual pH (8.9), you need to go quite a bit higher than baking soda can get you. As far as NH3/NH4 equilibrium changing at pKa 9.2, that shouldn't be an issue in an established aquarium. Nitrifying bacteria could be an issue, especially if trying to cycle a tank at that pH. Although, my understanding is that their growth rate is slowed, not that they can't function.