I'm about to set up my 75 gallon cichlid tank. I've heard that you
should put a piece of styrofoam under the tank to even things out when
it settles. My question is, how thick should this be? 1/2 inch, 1
inch?

Also, there's a centre brace on both the top and bottom of the tank.
Would I need to carve out a groove in the styrofoam so the centre
brace at the bottom could slide in? Not sure if the styrofoam could
break the brace or something under all that weight. The brace is
flush with the plastic bottom edge of the aquarium.

thanks in advance.