Yes it's safe, if you use it cautiously, a little at a time, and wait for the sodium bicarbonate to show its effect before you add more.
You're using bicarbonate of soda, not baking powder.
Because "bicarb" is soluble, it works swiftly and expends all its pH-raising power in one blast.
Along with it, you want another source of carbonates to steady the alkalinity and slowly raise the pH. That's why you also hear about "crushed coral" or aragonite, the same stuff that's used for "sand" in marine reef tanks. Just a little in the filter.
Sodium bicarbonate for the quick boost now. Aragonite for the long haul...