The minnows look like Fathead minnows. If you want to make sure that you are starting with a clean slate and nothing in in there that you don't want you could spread enough quick lime/hydrated lime to get the water pH to 11 or 12, and if you do it now the water will pH will have dropped enough by the Spring so you could stock fish.

Personally, I'd wait to see if it holds water first before you stock fish. Without using the clay that is there as a liner - compacting the clay and sealing the pond, you might not have a pond that is full and stays full. Time will tell.

Do a lot more reading on here about fish species and how well they do in Central Michigan. If you have a permanent inflow or outflow for water in the pond, you need to have a written stocking permit from the Mil DNR before you can stock fish. Any stocking company has to have a copy of that in their truck before they deliver the fish or they can get in the same amount of trouble as you can for stocking fish in a BOW that aren't permitted by the State of Michigan.

Get all the cover installed in the pond as soon as you can. It's easier to put it in a dry pond than a pond filled with water.

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