fed ex should be less then $50 to ship from maryland/PA to michigan.
Texas to OH was ~$50 fed ex standard overnight, 1 small box with 1 bag of 12 juvie mbuna.
Fish are also often shipped air freight the buyer picks the fish up at the airport. You could airfrieght them to yourself, then pick them up when they/you get there. I think its more expensive than fed ex though.
If you're going to be doing the shipping yourself, make sure when they're bagged they're bagged for shipping and pack them in the box properly.
Just a story about baggage handlers, I once tried to ship back a bottle of vodka from russia in my luggage. It was a hard plastic suitcase, and the bottle was glass and wrapped in clothes for padding. Still didn't prevent it from arriving in pieces. My luggage was checked and security sealed at the departing airport, no one was in it before I received it at final destination. Lord knows how hard they must have been handling the bag in order to bust it. I've seen other bags torn to shreds after being dragged (drug?) underneath baggage carts $100's of souveneirs destroyed... Moral is, nothing is safe in your checked luggage. If you can't carry them on, you're going to want to ship them for sure.