An example for the here mentioned responsible aquaculturists: an aquaponics system where the fish (here tilapia) and the plant (here kale) lives in a symbiotic system. Tilapia is a cichlid that eat plants or midge larvae and doesn’t need fish meal (other than salmon or trout). The by-products don’t pollute the surrounding ocean like in aquaculture but feed the plant in hydroponics via bacteria that cleans the water along the way. The system saves water and nutrients, but need heat and feed for the tilapia and light for the plants. Tiliapa and kale go to nearby markets and restaurants.
There are smaller aquaponics systems, as well: for fish tanks at home.