The removal process of ammonia (NH₃) to replace the bacteria in environments with a suitable substrate is better than systems based on bacteria suspended in the water column. Thus, the aim of this study was to study the efficiency of the wheat stem as a substrate to accelerate the consolidation of ammonia (Denitrification) and increase the chances of survival of Koi fish (Cyprinus carpio carpio) faced with the acute concentrations of ammonia. 8 glass aquariums were selected (the volume of 50 liters) and divided into two groups: control (no wheat stem) and treatment (with wheat stem, equivalent to 10% of the total volume of the tank) with four replications. 10 ml/l ammonia was added to each aquarium and its amount in the treatment and control groups were calculated after 24, 48, 72 and 96 hours. In the second stage, after adjustment stage, 24 Koi were divided into 8 new aquariums with an average weight of 6±2 g (different from the first stage). Fish were faced with a concentration of 10 ml/l ammonia for 96 hours. The mortality in the control group (have not wheat stem and have Koi fish) and the treatment group (have the wheat stem and have Koi fish) were counted in intervals of 24, 48, 72 and 96 hours. Results showed that the concentration of ammonia at the end of 96 hours in the treatment group compared to control group there was a significant difference (P>0.05). Also, the number of mortality in the treatment group compared to control group there was a significant difference (P>0.05); the lowest mortality related to treatment. The results of this study demonstrate the use of wheat stem in addition to increasing the efficiency of established systems of ammonia; increase the chances of survival of koi fish in the face of acute concentrations of ammonia.