In a clean quart jar, add the beets, ginger, zest and salt.
Open the probiotic capsule and sprinkle over the beets.
Add the water and stir gently.
Make sure all of the solids are below the water. If you have one, use a fermentation weight.
Loosely place a lid on top to keep anything from falling in.
Let sit in a cool place away from sunlight for 2-3 days.
Taste on day two. It should be slightly sour but in a pleasant way.
If it doesn't taste sour enough, you can let it sit for a couple more days.
Once it's to your liking, strain out the solids and put the liquid kvass in a jar in the refrigerator.
You can keep the reserved beets to snack on.