thank you kindly for the reassurance, MasK. it's not that i have anything against people cultivating probiotics in their kitchens! but some of what i was reading on line (for instance here:
http://en.wikipedia.org/wiki/Tibicos) was saying the bacteria strains can vary a lot, which makes sense, so i started wondering whether renegade bacteria sometimes get in on the act. but if that's not something i need to fret about, i'm glad!
if you can stand another question: one video i looked at mentioned making coconut-milk kefir by adding the contents of a probiotic capsule to coconut milk. can one do that with water kefir too, to add particular strains of bacteria to the population?
meanwhile, i'm in Poland. the need for a short postal trip is why i'd prefer to get my grains here, but if you know a good source in Europe, i'm open to importing them as well.
and thanks for taking an interest!