I started with a 1.5-2" Goliath in January 2017, chicxulubs thread on tank setup and flow of water helped me to get him onto frozen within the first two weeks.
Started him in a 50gallon tank, when he was 4" or so upgraded him to the 90gallon, and after two years the fish has grown to 13" eyeballing.
Avoid any tank mates that would be skittish in nature, avoid any tankmates that would be silver bodied, this is a fish that likes it's space, gets nervous if there are too many people near the tank, any sudden movements near the tank would trigger the fish into a suicidal mode, where the fish would crash and thrash all over the tank.