This bachelor’s thesis deals with the system which is designed as a pH regulator for aquarium water. The first and second chapter are aims to the basic requirements and possibilities on controlling of the potential of hydrogen in water. Main methods of the pH measuring, its controlling and regulation are included. The third chapter presents a design of the pH regulator system. The practical and software solution of this project is presented in the fourth and fifth chapter. There are described in detail the main blocks of the pH regulator - amplifier, galvanic isolator and output power stage. The results of the testing and measuring of the designed subsystems are introduced in the last part of the work