For some reason I just had a visual of some poor guy who’s job it was to follow the little fish and catch their little poop’s for fertilizer.
Does fish poop float or sink or is it water neutral?
I’ve seen these tanks made from chemical transport tanks with the top cut off. They pull water from the bottom loaded with the stuff plants like to water a raised garden while adding more water up top. The goal was to have plenty of fish and veggies to eat. I think the fish were trout in the one I saw. If it’s plumbed right it’s just a matter of opening and closing two valves.
All this happens in a greenhouse with climate control. For people who like to be off grid and self sustaining; it’s a good idea. Add a few hogs and chickens to breed and slaughter to have more variety in your diet and you have a mini farm. Get a milking cow if you want fresh milk but then you have another mouth to feed a special diet.
In California, they grow lettuce using wetback poop.
That’s got to be a wonderful smell.