I thought there were fairly large blackfly farming operations for fish feeding. maybe for non-ocean species? As with a lot of operational farming practices- it's probably a lot more complex than a few articles could easily encompass.
1. Black Soldier Flies
2. Duckweed
3. Algae (Omega 3s)
All of the above are strong protein sources and duckweed and algae are fast growers and high density producers (at least an order of magnitude more than soybeans).Obviously more effort is required to farm them but with automation it should require minimal labor.