However, the increasing value of ecologically pure food production has also led to a renewal of investigations devoted to the application of organic fertilizers in fish ponds.reported an increase in fish yields as a result of organic fertilization.investigated the increased oxygen consumption and water-quality deterioration at varying doses of organic fertilizer. Similar negative effects during the first month of dunging were also reported by Kwei Lin et al. (1999) when green weed material was applied. AdditionallyQin et al. (1995a) indicated that some kinds of manure delivered low nitrogen-tophosphorus ratio, which favors the development of inedible blue-green algae, leading to a decrease in fertilizing efficiency on the final product—fish yield. Therefore the application of organic fertilizers should undergo profound preliminary testing in order to guarantee the desirable increase in fish yield. In this case study we evaluated the effect of decomposed cattle wastes on fishpond plankton primary production.