Good tank size

Hi,

I found a video the other day of a guy keeping the following stock in a 150 Gallon tank:

X1 Great Barracuda
X1 Cherry Skunk Grouper
X1 Panther Grouper

I know he was incredibly over stocked, but his fish were amazing.
I was wondering how big of a tank is needed to house these fish. Not that I'm planning on buying any of them, just curious :)