well, its been a long long time. in high school i worked a few summers in a bait shop, that was also one of the largest live bait distributors in the upper midwest. i guess id have to start at where did the minnows come from, how long were they in transit, and how were they shipped. secondly i wonder how much water are you turning over? are your bait tanks constantly fed , or on a timer? we had at the time likely the last functional well in the city, and our tanks both in the store, and the large stock tanks out back were on a constant feed. chlorine/chloramines would be my biggest concern since you are on city water, followed closely by how many gallons an hour are running through the tanks. lastly water temp, as most baitfish sold does best in cooler to cold water. like i said, we were the main distributor for 5 states, and maybe every week and a half we lost a 5 gallon bucket worth of stock. as a side note, this brings back memories, if you ever wondered what the worst smell in the world is, you will find out if you are the guy who has to go out back dig a hole to bury the dead bait in. at the bottom of that week to two week old bucket is the worst smell you can possibly imagine.