Try this product: Bio-K. It's the only probiotic that's had an effect (immediate) on my gut. It's expensive, but worth it if it works. Try one unflavored bottle, all at once, and test it out this way. This Canadian company has done lots of trials on its product. The company determined that all the different strains of bacteria found in most probiotics actually end up competing with each other. So they reduced their product to two super-potent strains and called it a fermented dairy product, rather than a probiotic.

Milk kefir and water kefir -- yes, yes. And don't forget to feed them (prebiotic foods, etc.)