The present work aims to evaluate the efficiency of a biochar biofilter to purify the water of an aquaponic system according to the density of fish. For this, a unit has been set up at the Rural Engineering Department of the University of Dschang to conduct the tests. The biofilter made up of biochar based on corn cobs and pozzolan was set up as well as six columns of hydroponic system each connected to a biofilter and each containing three basil plants. The experimental device consisted of two densities DP6 and DP9 representing respectively the densities of 6 and 9 catfish per tank. Each density representing a treatment was mounted in triplicate. The fry were fed at 5% of their biomass at 2 frequencies (morning and evening). The physico-chemical parameters were measured once a day for the most part. Plant growth characteristics were measured on the 14th and 28th day after transplanting. Those relating to the growth of fish on the 28th and 46th day after loading. The results showed that the physico-chemical parameters of the water remained within the standard range required in aquaponics whatever the density, thus reflecting the positive effect of the biofilter. The DP6 fish recorded a higher weight gain of 15.26 g against 13.87 g for the DP9 after 46 days of rearing. As for the basil plants, those of the DP6 recorded the greatest average height of 30.88 cm. However, no significant difference was recorded between the treatments for either fish or plant growth. Subject to future work aimed at evaluating the functioning of the system over a relatively longer period, the installation of the biofilter makes it possible to increase the stocking density of the fish and, in turn, the yield.