Fish, like poultry, do indeed prefer to eat insects rather than grains. However I will present both here but I do highly recommend growing insects for supplemental aquauculture (and poultry) feed. Bill Mollison also recommended this technique and can be viewed in the Aquaculture chapter of The Designers Manual on page 492. I myself have cultured insects and seen zealous response from fish and poultry with these fairly easy systems of growth. The unique thing about the culture of insects is that they are virtually all protein where as commercial or even homemade feeds are a mix of proteins and carbohydrates when grains are the main component of the feed. Also food scraps present this composition of a mix of proteins and carbohydrates and are often fed to chickens as well. However they can be upcyled with other life kingdoms with the final product being a high quality feed with very little inputs: maggots. Not only maggots can be cultured while taking advantage of easy to harvest waste streams.
Black soldier flies, raised on moldy acorns, dog manure, and the chickens' own manure, as well as coffee grounds and a few other otherwise inedible things around the place; supply much of my layers' protein feed through a few months of the year. I imagine they can serve as well for fish, provided they are big enough to eat them.....
Alder Burns (adiantum)
If tomatoes are a fruit, then ketchup must be a jam. Taste this tiny ad:
It's like binging on 7 seasons of your favorite netflix permaculture show