I made beet kvass from the recipe in Nourishing Traditions. It's been 3 days, and there's a layer of mold on the top. I've tried to skim it, but it's hard to get all of it, and it's still there. I tasted it, very strong, salty, sour... quite nice actually. But the mold is bothering me. I strained the mold before drinking. Is that enough? Or is there a way to make this without the mold forming?