I have an older Igloo water cooler I use with just a bubble maker in it. It will keep a few lbs of minnows nice and frisky all day long. Without a pump recirculating water, shad won't last long if there's very many it. Better than a 5gal bucket with nothing though. I plan on putting a pump on it with a good filter, just haven't had to have it yet.
If you're not living on the edge, you're taking up too much space!