This article studied a chemically activated carbon prepared from melon shell with KOH as an activating agent. The sample was analyzed by FI-IR, BET, EDX and SEM. Effectiveness and Potentials of the prepared Melon Shell Activated Carbon (MSAC) and the influential factors like adsorbent quantity, initial metals ion concentration, pH, temperature and contact time were as well examined. The process was found to be reliant on all the considered factors, with optimum removal of both metal ions at pH 6.0. The respective adsorption capacity (Langmuir monolayer) for both Fe(II) and Mn(II) ions were found to be 3.148 and 3.706 mg/g respectively. The Langmuir isotherm better described the experimental data. The adsorption kinetics and equilibrium were also better described by Pseudo-second order for Mn(II) ion while none fitted for the uptake of Fe(II) ion. Similarly, thermodynamic parameters such as DG0, DH0 and DS0 were evaluated. The negative value of ΔG0 along with the positive value of ΔH0 and ΔS0 indicates that the process is spontaneous, endothermic and an irregular increase in the disorderliness at the solid/solution interface of the adsorbent during the process. The results shows that activated carbon prepared from melon shell has potential for the treatment of wastewater from fish farms.