Chloramines are residuals of chlorine. Chloramine T (Cl-T) is a low toxic disinfectant used in aquaculture against external bacterial infections and parasitic infestations. Toxicity of any chemical is species specific. Therefore in order to understand the sensitivity cultivable aquatic organisms, this study dealt with acute toxicity of Cl-T to the common carp Cyprinus carpio fry and the giant river prawn Macrobrachium rosenbergii post-larvae (PL). The 96 hr LC50 of Cl-T was found to be 24.677 mg/l and 7.650 mg/l to the fry of C. carpio and the PL of M. rosenbergii, respectively. Abnormal behaviors such as erratic swimming, loss of balance, gasping at the water surface, excessive mucus secretion over the gill chamber, jumping at the water surface, lethargy and gill hyperventilation, and morphological changes like loss of scales, ocular opacity and skin darkening were seen in the test fish. In the test prawn erratic swimming, loss of balance, excessive mucus secretion over the gill chamber, jumping at the water surface, lethargy, gill hyperventilation, and whitening of the body were seen. When comparing the LC50 values of Cl-T to the fish fry and prawn PL, it is concluded that toxicity of Cl-T is species specific.