A marine aquarium was established at Annamalai University 30 km away from the coast with recycled seawater system. The problems faced during the operations were increase in water temperature, consumption of dissolved oxygen and evaporation of seawater. The rate of evaporation of water in entire aquarium was estimated about 128 liters/day. The temperature increase in the aquarium tank was observed as 0.1ºC due to the operation of canister filter, 0.1ºC due to pumps and 1.1ºC due to aquarium lightings. Further the position of aquarium lids leads to a raise in temperature of 0.5ºC. The consumption of dissolved oxygen by eight band butterfly fishes Chaetodon octofasciatus was taken as a case study and found to be 2.031x10^-4 ppm/g of biomass. The optimum stocking density for balanced dissolved oxygen condition was calculated as 0.919 kg of biomass / 1,000 liters of seawater with the aeration of 0.351 ppm/hr.