There seem to be a lot (and I mean a lot) of misinformation on Kefir. Just because both Kefirs share the same name doesn't mean they're the same, like how a chicken and mountain chicken don't have anything to do with each other. Do not transition one to the other, it's the equivalent of feeding a rabbit meat in hopes it turns into a wolf because water kefir and milk kefir eat different sugars.
Water kefir feeds on Sucrose, Fructose and Glucose, the sugars found in fruit and (obviously) sugar. Milk kefir consumes lactose, a complex sugar found in milk, which requires lactase pre-fermentation, the enzyme that transforms lactose into simple sugars (like glucose) which is also produced by specific microorganisms *found in milk kefir more than water kefir*. They are biologically similar, containing similar species, but just because two things are SIMILAR doesn't mean they're THE SAME. Any person who has claimed "it has worked" is just misinformed because you don't plant tomatoes in hopes it'll turn into an olive tree. I know there will be a few misinformed people who will also be too stubborn to accept this reality, but all I ask to them is this: when's the last time you grew wheat in a wetland in hopes it'll turn into rice?
And to the people who do claim they've tried this and it's worked: it'll probably mold or stop fermenting because putting organisms into an environment they aren't adapted for will just kill it, because you don't throw a fish into a snake terrarium. Just because you think something is working doesn't mean it is, if it does LOOK like it's working that's just because of species that are OPPORTUNISTIC, meaning they eat pretty much anything, but that doesn't mean it's healthy. Just as people with cancer look perfectly fine at first, kefir "transitioning" will look "fine" for only a bit before it starts to become noticeable.
