Differences between refrigerator ice and purchased ice?

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I have two problems with "refrigerator ice". 1. It's milky looking and not clear. 2. It reacts with Coke to create an overflow of "fizz". This releases the carbonation and makes the drink "flat" tasting. Why does this happen? Can refrigerator ice makers be adjusted to make them more like purchased ice? Well, I prefer purchased ice in a bag because it is usually clear -- and doesn't cause Coke to overfizz. And you........?