Baking soda is the go-to for alkalinity without spiking pH.

Yes, that’s exactly what it’s for.

Baking soda (sodium bicarbonate) has a pH around 8.3, which is mild. It raises total alkalinity—the water’s ability to buffer pH changes—without sending the pH into the stratosphere. In pools, this is standard practice: you add baking soda to bump alkalinity, and pH barely budges. In aquariums, same idea.

The alternative is soda ash (sodium carbonate), which is alkaline enough to jack pH up fast. That’s for when you want both alkalinity and a major pH shift. Baking soda is the steady, predictable option.

It does move pH a little, just not a lot. If you add a big dose, expect a small bump. But for most situations, it’s exactly what you want.

Just test after adding—don’t guess.