I expect water with my minnows, I consider it a package deal seeing how they need water to survive. If your talking a big 30 quart Engel it may be easier to carry a 5 gallon bucket into the baitshop. You could buy some Better Bait add a pinch to a couple gallons of tap water, carry a bucket in get your minnows with 3 or 4 gallons of water and put them in your cooler. If it's a 19 quart I wouldn't have any issues asking them to fill it up. I use a 5 gallon bucket and never had any problems with any baitshop giving me water. I've had to ask for more a couple of times sure, but it's rare.
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