Why Sodium Carbonate is not using alone but usually with Sodium Bicarbonate?

[thejacgues]

Hey,

I've noticed that common alkalinity maintaining products use either only sodium bicarb or a mix of the two.
Why Sodium Carbonate is used so rear and why never alone?

 

[Randy Holmes-Farley]

Hey,

I've noticed that common alkalinity maintaining products use either only sodium bicarb or a mix of the two.
Why Sodium Carbonate is used so rear and why never alone?

It is often used alone. Both my DIY recipes (BRS uses them) and the original B-ionic from ESV are carbonate.

I think some companies use a mix for two reasons:

1. They want to make it seem like their more expensive product is "better" than just carbonate based products.

2. They focus on pH effects, perhaps misunderstanding them or intentionally misleading reefers about them. There is a ratio of mostly bicarbonate and a little carbonate that will not immediately have any impact on the pH of seawater. What that ratio is depends on what the pH of the starting seawater is.

IMO, most reefers are best off with a pure carbonate, or maybe even hydroxide-based two part, depending on the pH in their aquaria.

 

[thejacgues]

Thanks @Randy Holmes-Farley . I read that for maintaining it's okay to use carbonate only, but when rising kH, the mix is a better choice. Is that only due to an effect on pH?

 

[Randy Holmes-Farley]

Thanks @Randy Holmes-Farley . I read that for maintaining it's okay to use carbonate only, but when rising kH, the mix is a better choice. Is that only due to an effect on pH?

I don’t think this is generally true, but if you need a big rise in alk and do not want a pH boost, then bicarbonate, or mostly bicarbonate and a little carbonate, is the better choice.