Solarpunk

While you're not really wrong (most waste management systems are trying to emulate natural processes using less resources, whether they be space, time, energy, or maintenance) the core idea discussed here was initially studied in the 80s, so also decades old. It's not that it is innovative, it's that it was set by the wayside when simpler growing techniques such as hydroponics came along. Of course, those simpler techniques don't have a waste management system built in.

I skimmed this paper, but it's interesting.

One thing to note, is that their salinity (ECs) are good, but not great. Generally, you want them under 2 dS/m in growth media. 3-4 is considered fair, but with some limitations, so they might have to refine their desalinization process a bit more, or you know, use freshwater fish.

The N input from the fish manure (I feel weird just typing that) is actually pretty good. About 100 lb/ac, which is the upper limit requirement for most crops. They would most certainly need P amendment, though, and that could cause a lot of issue with their aquaculture if it makes its way into the system.