There is only one fan at the back plus the one from the power supply unit. I have 3 in the front. I have installed a radiator with 2 fans at the top. But 3 also fit in there. Just be careful! The case is only partly suitable for water cooling. The waste heat cannot escape from the top, my top cover always gets 60°C because the ventilation slot is far too small. So it's better to work with tower cooling so that it can "ventilate" from the front to the back.