Efficient conversion of feed is the foundation of profitable aquaculture operations. Feed conversion ratio (FCR) is a production metric commonly used to compare efficiency by both researchers and producers. Final production FCR values are heavily influenced by fish mortality, the timing of fish mortality, and wasted feed and these factors overshadow determinants of feed conversion at a physiological level, otherwise known as feed conversion efficiency (FCE). We measured the effect of certain biotic and abiotic factors on FCE in Channel Catfish (Ictalurus punctatus), including dissolved oxygen concentration, stocking density, dietary protein, strain, fish mass and sex. The best performing juvenile channel catfish had an FCE of 0.93 up to 120 g, but increased to a cumulative FCE 1.10 once they reached 730 g. Higher dietary protein concentration improved FCE across size classes and seems to have the largest impact of all factors tested. Dissolved oxygen concentration between 25-150% had no impact on FCE, only feed consumption. Density had no effect on FCE or feed consumption, whereas strain may have had a weak effect on FCE. Males had significantly better FCE than females across the sizes tested. Increasing dietary protein and being male are the two factors tested that had the greatest improvement on FCE, while most factors had no effect. The potential physiological growth performance of catfish is much greater than what pond culture reveals.