Any baitshop worth a darn will be able to bag your minnows and shoot some oxygen into them. I don't allow them to put more than a quarter pound per bag in and will buy two to three bags. I keep two unopened bags in one livewell, open the other and in the summer, it's a must to keep just 6-10 in a small bucket to use for fishing while keeping the rest over the side of the boat in a perferated minnow bucket. The frozen water in a bottle works, but, it thaws so fast it's almost not worth the trouble unless you bring an ice chest full of frozen bottles. I keep a couple of small ice cream buckets to keep a few handy while fishing. This way, you don't end up having several die at once. If you have enough room in your ice chest, stick the extra bags of minnows in there and they will last in good shape for a day or two until you're ready to use them.