I use litmus paper to test acidity of the brine. Usually ends up around 3.0-3.5 ph. Also monitor smell, bubble formation (good) and watch for bad colors (white

I use litmus paper to test acidity of the brine. Usually ends up around 3.0-3.5 ph. Also monitor smell, bubble formation (good) and watch for bad colors (white, black, green mold on top), browning of ferment, especially near the top (bad)