Yes, it's knowing the requirements of your fish and how to maintain their habitat. That 1" to 1 gallon rule is not very accurate either. It's a guideline for those who are starting out. Once you get your feet wet so to speak, you (in theory) learn more of how to maintain your fish and the aquariums.
Also, larger fish like that are in larger bodies of water, which allow for much more ease of maintanence. They don't need water changes, they're pretty much self-cleaning and regulating. At 2400 gallons, the biggest concern is "topping off" the water volume.