Filling empty space in carboy?

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How do these look for filling empty carboy space/weighing down dry hops bags? I am kind of worried about them being safe for putting in my beer. Having a hard time finding american made clear glass marbles. I am pretty sure they are made by an American company. But, they are also covered with an "opalescent finish" not sure if that would affect the beer or not. They are cheap and easy to find though, which makes them tempting. Thoughts anyone? I'm going to make a trip to michaels before I do any purchasing.

CO2 will fill the head space in your carboy I did 2 gallons in a 5 gallon no problems with oxidization at all. As for the dry hopping as long as what your dry hopping with touches the beer you should be good it shouldn't need to be fully submerged. If I were you I'd consider using a steel mesh container designed for dry hopping these can be made very easily. I wouldn't mess around with the marbles who knows what they are coated in and if that will come off once alcohol is present.