I got some grains from a neighbor and am attempting to make water kefir. My first batch turned out great — I did a second ferment and it turned out nice and fizzy. I did two jars for the second batch and one of the jars developed a thin white film on the top. There are also a few large bubbles there all the time, not just if it gets disturbed (not the small kind that come from fizz). It smells fine and when I swirled the jar, everything looked normal, though it did settle back into the center of the jar after a while. I did some research and determined that this can be a sign that the grains need to be rehabilitated. I don’t need to salvage the grains as I have loads of them from the other jar, but I’m wondering what might have gone wrong.
I’m using a mix of sucanat and a white dried sugar cane sugar, with Berkey filtered water (which has alkalizing rocks in it). The grains from my first round multiplied like crazy — from about 2 tablespoons to over 1 cup. We have very hard water, with loads of minerals -- Berkey filters apparently don't remove minerals. I've read somewhere that some people have trouble with Berkey water, but I don't want to use our tap water, as it seems to be quite impure (if I water our plants with it, they get musty no matter what I do, and if I wipe the table with it, it starts to smell really odd). Coulc it just be the Berkey water?
I tried again with the grains from the jar that looked good and now the film grew on those jars too. In one jar I used just sucanat, and that one looks much more filmy, with some large bubbles. In the other jar, I used half sucanat and half white evaporated cane juice. That one doesn't have so much of a film all over it, but what looks like the same filmy stuff has left a thick ring around the edge of jar, where the top of the liquid meets the jar. This second round I put in the oven with the door partly open, with the oven light on, because we live in a cold climate my house is getting cooler (64 degrees and a bit less at night and somewhere around 68 in the day).
I read the problem could be contamination, too high of a mineral content in the water (but that makes grains slimy and mine are not), overcrowding (but the jars in my first try had the same proportion of ingredients), or a lack of nutrients (but again, the jars were the same). I've been using about 2 TBSP of grains with 1/4 cup of sugar and 3 cups of water.
Is the batch with the white film okay to drink? It doesn’t look like mold …
Any ideas on what is going wrong? Or is this normal?