I'll make a very quick one and say that when you put a million animals in a very tight space, with no biosecurity in the ocean, you will get rapid development of bugs, pathogens, disease, and whatever. By going to closed containment, we are afforded an additional benefit. We treat all our water on an hourly basis as it recirculates, with ozone and UV, so any parasite that would perhaps come in by accident—and you have to be prepared for that to happen—is immediately killed and not allowed to propagate.
Furthermore, because of the environment being so contained, salt—and you'll hear this when you visit the Freshwater Institute—can be readily utilized as a very good therapeutant, and salt is as natural as it comes.