The AT-Control System Set is a centralized, modular, microprocessor controller for aquariums, terrariums or other applications. AT-Control can measure and control pH, ORP (Redox potential), temperature, conductivity, water level and using the numerous timed circuits, lighting, dosing etc. Programming and control can also be undertaken using a PC via an USB connection. The system is modular in arrangement. It can be enlarged from a basic module to a complete control unit for several aquariums. All the modules are interconnected via USB ports. The data can be downloaded to a PC and shown graphically.