There are some scientists and activists who have developed a very low-cost, self-contained system for raising mass quantitites of fish for human consumption without immense fish-food requirements. The idea is to build such urban on-land fish farms in areas where protein sources are not abundant and fishing the old fashioned way is not viable because of low aquatic population, unsanitary water, or simply no available natural aquatic ecosystem. See the article here:
I don't mean to speak blasphemy but this seemed like a good idea for cost-efficient sustainable food sources for communities in need of healthy protein sources. I realize that fish are still animals and it probably isn't super fun for them to get eaten, but there are some places in the world where varied beans are not an option and omega-3 or B12 supplements are just too expensive. In such situations, the not-too-nasty fish proteins may be a blessing to the community.