Just depends on what warm water fish you are feeding and what results you desire. For instance, when grown at 80 F, fingerling Hybrid Striped Bass growth varied significantly, depending on both type and content of dietary protein and content of fat. Catfish formulations are plant based, while good trout/salmon formulations are animal based (preferably fish based). Strictly carnivorous fish do not do as well on plant-protein based diets. Below, diets are described in terms of Protein/fat, so a 40/10 is 40% protein and 10% fat (the OLD reliable trout diet).
36/8 (plant based)... 280% Weight Gain X
42/4 (plant based)....347% " 1.24X
35/10 (fish based)....432% " 1.54X
44/8 (fish based)....487% " 1.74X
55/15 (fish based)....650% " 2.32X**
It is important to note that all of these diets were high quality, they were just designed for different purposes and vary greatly in cost. For instance the 36/8 is designed for channel catfish fingerlings and the 55/15 is designed for Atlantic Salmon fingerlings. The 55/15 may cost 4 times as much as the plant based 36, so the economics are certainly arguable... just depends.
**Additionally, the ultra high growth on the 55/15 should be taken with a grain of salt as it resulted in obese fish (HSB very efficiently lay down dietary fat in their abdominal cavity), indeed the whole-body fat of HSB fed the 55/15 was 62% greater than that of the fish fed the 42/4.
Lets revisit this topic on LMB this fall as Bob Lusk is working on a trial this summer that should give us some more to discuss. Mark
