We studied the practical use of seaweed to remove inorganic nitrogen, especially ammonia-nitrogen, from the intensive shrimp culture ponds in developing countries. At first, we considered and experimentally evaluated the performance of ammonia-nitrogen uptake by seaweed in terms of parameters essential to the designing of intensive mariculture ponds. Based on the mechanism of ammonia-nitrogen uptake by seaweed, it was predicted that the ammonia-nitrogen concentration in the shrimp culture pond could be controlled by keeping it lower than a certain limit of value using a sufficient amount of seaweed with a condition that the rate of ammonia-nitrogen generation was constant. Experimental ammonia-nitrogen uptake runs confirmed this prediction and gave the parameters essential to design the culture pond with seaweed. Secondly, the control of the pond water quality for the practical shrimp culture batch was simulated by simple calculation based on the material balance of ammonia-nitrogen with parameters obtained from the experiments. The concentration of ammonia-nitrogen could be favorably controlled using seaweed in the practical batch and this method found to be feasible. Consequently, the water quality control using ammonia-nitrogen uptake by seaweed was proposed as a simple and convenient method appropriate for the intensive shrimp culture pond in developing countries.