Abstract: To explore the potential process of growth heterogeneity in discus fish, this experiment selected five pairs of the same species of discus fish as parents and cultivated their offspring for 60 days. The offspring were divided into two extreme groups with significant differences in body weight: the slow-growing group (S group) with the weight of (0.153±0.011) g and the fast-growing group (F group) with the weight of (0.347±0.030) g. After 30 days of cultivation, the growth, nutrient digestion, carbon and nitrogen balance, and transcriptome analysis of the visceral tissue of the discus fish were measured. The results showed that, in terms of growth, the average daily weight gain , average daily feed intake and feed efficiency of the F group were significantly higher than those of the S group. In terms of digestion, the apparent digestibility of dry matter, carbon, and nitrogen in the F group were significantly higher than those in the S group; the activities of α-amylase and gastric protease in the viscera of the F group were significantly higher than those in the S group. In terms of carbon and nitrogen balance, the F group absorbed more carbon and nitrogen, mainly for growth, and excreted less carbon and nitrogen through feces and respiration/excretion than the S group. Transcriptome analysis showed that the differentially expressed genes between the two groups were mainly enriched in signal pathways such as myocardial contraction, calcium signaling, glycolysis/gluconeogenesis, PPAR, thyroid hormone, purine metabolism, insulin secretion, galactose metabolism, and the pentose phosphate pathway. Among them, the significantly upregulated genes in the F group included ann, mid1, pur, fat, elo, acy, and dcK, and the PPAR signaling pathway and purine metabolism may be related to the rapid growth of the F group. The results indicate that compared to the small-sized discus fish, the large-sized individuals have stronger growth and digestion abilities and higher utilization of carbon and nitrogen, which may be related to the activation of the PPAR signaling pathway and purine metabolism, providing a theoretical basis for the nutritional intervention and breeding of allometric growth fish.