The best protein for fish is the one that most closely replicates that specie's amino acid profile. That is why fish meal is the gold standard of products for fish that eat fish. For fish that eat plants a plant-based source is good.
If you want to know more then look at this post by Mark Griffin PhD nutritionist and former head of Purina's feeds program.
https://forums.pondboss.com/ubbthre...gold+standard&Search=true#Post244349However, the science and understanding of fish food components is evolving and there are new products - see PB mag.
