It is possible, through buttons for user input and an LCD display for output, to choose the aquarium's ideal temperature, which is set by a fan and an aquarium heater, controlled by an arduino.

There are three temperature states for the aquarium: Cold, in which the heater turns on and the LED blinks blue; Ideal, in which the arduino only monitors the temperature and the LED blinks green; Medium-hot, in which the fan works at half power and the LED blinks yellow; and Hot in which the fan works at full power and the LED blinks red.

project's video: https://www.youtube.com/watch?v=hnH99Ou-5S4&

obs: This project was developed by a first-semester student of computer science