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Abstract

Tank hygiene is an essential aspect for successful fingerling production but can involve substantial workload to maintain. The purpose of this research is to develop and test a new version of a flow-driven, self-rotating tank deposit remover to automatically and quickly remove the deposit for grouper nurseries. The deposit remover has a suction tube lying on the bottom of the tank. Water flowing through the suction tube drives a propeller to rotate the tube while sucking up the solids on the bottom. Previous versions of the deposit remover suffer from incomplete solid removal and a long operating time. An integrated nozzle/ scraper assembly is introduced to improve the water inlet of the suction tube. A new gear box is designed to reduce the footprint by one-half and to align the input and output shafts for better balance. Modifications are made to the pivoting pipe elbow to achieve a uniform spacing between the suction tube and tank bottom and to eliminate solid accumulation surrounding the pipe. Optimum configurations of the propeller and the scraper are determined by experiment. The results show that the new deposit remover could remove more than 93% of size 0 and 3 feeds in one turn and could remove all the size 0 feed in 4.3 min and size 3 feed in 2.6 min at a flow rate of 1.77 L/sec. The removal speed is five times faster than the previous version making it a practical tool for the automatic bottom cleaning of grouper nursery tanks.

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