Why would you make a thread like this if you haven't built it yet? And you plan on keeping this outside in Michigan? Well you could get a heater for it but after your power goes out when it's cold you'll lose everything in a few hours. Your options are bluegill, bass, or sunfish, have fun with them! Unless of course you could factor in a generator and gas in your $300 budget.
I also think it would be stupid to build a 4'x4'x'3' tank when you could just buy a rubbermaid stock tub for less than $200.