Aquaculture 4.0 is characterized by the use of digital technologies integrated and connected through software and intelligent systems (e.g., Internet of Things) to improve production processes and support producers' decision-making. In the context of aquaculture, the use of aerators is important to ensure dissolved oxygen levels in the water, increase fish yield and reduce mortality. However, the lack of control in the use of aerators without proper dissolved oxygen sensing by small and medium producers results in high energy costs in production. This work aims to develop an energy-efficient system for managing aerators, utilizing IoT technology, applied to aquaculture farm nurseries. The proposed system comprises dissolved oxygen, pH, and temperature sensors, controlled by a microcontroller that receives real-time information and regulates the power of the aerator motor, maintaining a predefined dissolved oxygen limit. All information is remotely monitored through a dashboard. The system was evaluated in a real aquaculture scenario and achieved a reduction of up to 64% in electricity consumption.