There is more than one way of feeding carnivorous fish: Surubim (Pseudoplatystoma reticulatum x P corruscans) are able to cope with carbohydrates rich diets, but there is a trade-off between growth and immunity

•Higher dietaty protein concentrations did not result in greater performance gains in surubim.•Different protein-to-carbohydrate ratios can lead to different growth responses and different ways of improving yield.•Surubim are able to cope with high carbohydrate diets, but there is a trade-off between growth performance and immunity.•The immune system rather than body size are affected in surubim with a lower dietary protein concentration.