Abstract: To address problems of time delay, nonlinearity, and susceptibility to environmental interference in ammonia nitrogen control for small and medium sized fish and shrimp aquaculture, a fuzzy adaptive PID control algorithm has been designed to realize intelligent regulation of aquaculture water quality．Based on nitrification reaction mechanism analysis, a first-order inertia model with pure time delay has been established, with aeration rate as input and ammonia nitrogen concentration as output．Model identification was performed using one-site step response tests and tangent method．A two-dimensional fuzzy inference system was constructed with ammonia nitrogen concentration error and its change rate as inputs and PID parameter correction values as outputs, realizing online adaptive parameter tuning．Step response and anti-interference simulations were carried out in Matlab/Simulink．Results have shown that compared with traditional PID controller tuned by Ziegler-Nichols method, proposed algorithm reduced system overshoot from 25.2% to 16.5% and shortened settling time by 32.2%．Under disturbances such as feeding and rainfall, it exhibited smaller dynamic deviations and faster recovery speed．This algorithm features simple structure and low computational cost, allowing it to be deployed on low-cost PLCs．It has provided a feasible, user-friendly, and economical intelligent solution for precise water quality regulation in small and medium sized aquaculture．