Objective To provide solutions for sealing and installation inconvenience of the automatic aerator during breeding of mandarin fish.

Method Through the whole cycle of mandarin fish breeding starting from July to November in 2014, fishponds tests were performed to study the cleaning cycle, measuring accuracy and controlling reliability of the automatic aerator. The impacts on aquaculture water quality and electricity consumption were evaluated. The sizes of the O-shape sealing ring and the triangle slot were changed to improve the sealing and installation convenience of the dissolved oxygen (DO) sensor. The sizes of the upper and lower chamfers were also changed to improve the installation convenience of the DO sensor.

Result During the whole breeding cycle, the average cleaning cycle of the automatic aerator was not significantly different compared with the Denmark OxyGuard DO monitor. The error of measured temperature was ±0.8 ℃, the error of measured DO content was ±0.6 mg·L^-1, and the DO content of the controlled fishpond was higher than the set lower limit of 4 mg·L^-1. Compared with manual control, the DO content of the controlled fishpond using the automatic aerator was higher with a peak value of 7 mg·L^-1, the average ammonia nitrogen content in water was 35.9% lower, the average nitrite content was 50.7% lower, and the electricity was saved by 29.5%.

Conclusion The automatic aerator is highly resistant to stain, can be conveniently cleaned, improves water quality and saves electricity during long-term use, meeting the requirements of the fishpond management. The automatic aerator has good sealing and can be conveniently installed, thus it is recommended for large-scale popularization.