In many regions minnows are a very important bait for fisherman. Many bait machine owners sell minnows in their machines. And make good money doing so. To do so you must have some kind of holding tank to keep your minnows. New minnow tanks are very costly but I have been telling people for years they can start out by building their own holding tank at a very low cost. You need several things to keep healthy minnows, cool water, aeration are the most important. You will also need to keep your ammonia level in check. I have helped many customers over the year do this by getting a chest freezer to start. The inside of the freezer needs to be seamless inside or you will need to seal any seams so the water won’t leak. You will also need a electric timer so you can set the temperature otherwise you would have a big block of ice. You have the timer set so the freezer turns on and off keeping the water from freezing. Some freezers I see have a drain hole at the bottom, you would want to set that up with a shut of valve so you can drain down to replace water. If there is no drain and you have to siphon out the water, always remember to put the hose at the bottom, all the bad water lays in the bottom of the tank. Last you can keep the ammonia in check by keeping a pound or so of zeolite in the bottom of the tank. This can be put in a nylon sack tied off or cut off the bottom of a pair of panty hose and tie off which works great too. This will need to be replaced about once a month, a little sooner if you hold a big amount of fish. Don’t throw away the zeolite as this can be reused after recharging. To recharge simply wash thoroughly then soak in saltwater for 24 hours, then rinse and your good to go. You can purchase zeolite by calling Matt Kurtz at Kurtz Fish Hatchery at 484-364-6044. This is the same stuff that keeps the minnows alive in the cups in the Sportsman.
Check out these two videos I found on YouTube, these will give you a idea on how to do this. Also if you wish to buy a reasoable priced minnow tank here is a good place to start. http://www.piedmontbaittanks.com/