@endless---1/2 ____ of grains? cup, tablespoon? I would bet your ratios are off, 1 pint of water would need just 2 tbsp of grains and 2 tbsp sugar. Usually within 48hr at 70-72F alot of the sugar has been utilized. But there are many variables: adjustment period for grains, quality of water, nutrients/additives, temperature, ferment with access to oxygen recommended, etc.
Water grains (WKG) can be used in milk since they contain several lactobacilli strains, but you will get a different product then fermenting milk with milk kefir grains(MKG). And the water grains really need to go back to a water-sugar solution for 24-48hr to maintain them, they just do better. Milk grains can also be converted to ferment pure juice/nectar/sugar water (many long time kefir makers call these "transmogged milk grains")--but they do not need to go back in milk since they have an adjustment phase (just use excess MKG), they will not grow without lactose, but should kefirize you juice/nectar,etc. for a good 6-9 months before they die. There is a "kefir starter" on the market--these are not grains but a powder that will typically make up to seven batches--this starter also does not contain the same organisms that the grains will produce.
In regard to cloudy water when using WKG that is normal since they are introducing yeast among other things. If your water:grain:sugar ratio is off your grains may not grow well (mine double in weight every 2-3 ferments) and they will not make a nice kefir. Improper ratios commonly produce a thick or slimy water.
Ideally you use 1 cup good water (spring, mineral, hard well): 1 tbsp grains: 1 tbsp sugar. Do not use RO or distilled water, avoid chlorine and sulfites. I usually make 3-4 cups each batch: I always add 1/4 lemon (for every 3-4 cups water)-do not squeeze until grains removed, 1 dried sulphur free fig or 5-10 sulphur free raisins plus 1/8 tsp blackstrap molasses (molasses every other batch). The only other thing I add in primary is chunks of ginger or hibiscus or other citrus (have found grains can get damaged..ie mushy--dying). Cover with breathable cloth, place in cabinet/counter corner away from sunlight and taste in 24hr, in 48hr--strain when enough sweetness is gone, squeeze lemon into the grain-free water kefir (or you can use in next batch). You can now proceed with the secondary (flavor) ferment. To the fresh WK, you can add tea, juice, concentrate, fruit, herbs, etc. Cover with lid, place on counter for 24hr (or until first bit of foam develops is fruit was used) and then transfer to refrig. The sealed container will start to carbonate, if you want still WK just twist the lid open a tad so the CO2 comes out. Just like any ferment you risk bottle bombs if you leave at room temp in a sealed container for too long--use caution and common sense.
Here is a very active Yahoo kefir forum: http://groups.yahoo.com/group/Kefir_making/
Great source for grain sharing, advice, recipes, etc. And then the "father of kefir, Dom in AU": http://users.chariot.net.au/~dna/Makekefir.html
History, studies, recipes, list of organisms, colony counts, all you want to know.
Sorry for long post.