Our outdoor tanks have a constant temperature system.Customers can choose an ideal temperature between 20 to 45centi degree according to their will. This setting temperature will display on the lower right corner of the computer board, the number in the middle on the board is the actual temperature inside the tnak, when the actual one reaches the setting one, the heater will stop working and will not resume till the actual one becomes lower than the ideal temperature, and now only the water circulating pump is still on. This progress will go on and on, and that is the working mechanism(机理) of our product.