Practiced for millennia.
Back in the day when we were starting up Western aquaculture IMTA used to be called poly-culture. The FAO promotes this big time in developing countries.
Growing shrimp (or marine insects) in ponds in the tropics has always meant managing biodiversity in the ponds. Algae and bacteria being the majors primary cultures that need to be managed to get the end product out. Yes shrimp is just the sum of these cultures as a centre of the plate protein offering for end consumers. After all cannot serve up algae and bacteria (yet). Algal/bacterial culture technology is something that we had to develop and grow in tandem with shrimp aquaculture.
Indoor RAS technology has meant that one can remove all externalities and concentrate on direct feed conversion. No more worrying about managing and growing a population lower down the food chain to grow one further up the food chain. However it has its own problems too including how to scrub the discharges.
The move of the aquaponics concept, using RAS technology developed over 30 years ago in Europe, to urban USA has meant a re-naming to something more scientific high level and tech sounding. Polyculture is just not sexy enough and brings to mind extensive outdoor systems in developing countries. This just does not tickle investors.
Of course this is great technology, is sexy and feeds into latest food production concepts (local, circular economy, IoT, zero antibiotics, sustainability, etc, etc) and is advancing on many fronts in many countries.
BUT it is still extremely niche and will not help solve the feeding of the near future population growth on this planet. It is riding on the coattails of mono-culture aquaculture which, as a non-peaked resource can and has helped to date to offset a stagnant peaked resource that is fishing – you all have the graphs.
Perhaps IMTA will really go mainstream by 2050 once our population has peaked and we have covered the planetary food security issue, and increased healthy seafood consumption while, with stewardship, protected the oceans from further pillage.
Until 2050 then…..although, by then, we will probably be eating shrimpless shrimp made from algae or bacteria directly!