Shall I go first, Craig?
The first question was the notion of multiple fish in one tank. That's not quite correct. If you get the time to look at the report, it's multiple cohorts in the same water volume or same treated water volume, but they're actually separated into growth classes in different tanks. Small fish never meet big fish. That is called sequential harvest, and it's a technique that's used in all the other closed-containment fish farm species, to keep the loading on the biofilter the same.
What is required is good biosecurity protocols when you bring your new smolts in, that they don't bring disease in that then wipes out the whole of your farm. So you have to have a holding tank to do that biosecurity. That's quite standard practice in the existing closed containment industry.
I wager I'm probably the only person in the room who's eaten land-based--