Don't let the haters get you down!
My suggestion is that you don't worry about the heat. Make the top of the arcade self contained, but also acts as the lid, like this:
or this:
And mount the whole self contained top onto your cabinet which contains your aquarium. You'll need access for cleanings, feedings, etc anyhow, so you'll want a quick and easy way to perform that on the fish tank and you'll want a way to remove the top so you can work on the cabinet when components fail.
Do I think this is a good concept? Who cares, it's yours. Have fun.