The Pro Clear Aquatic Systems Red Flex Reef Sump - 400 is a highly efficient sump system designed for saltwater environments and features a modern red and white design.. Water from your aquarium flows through two separate overflow ports, into heavy-duty bubble diffusers and then through a 4 inch, 200 micron filter sock to ensure that any harmful particulate matter is removed. In case of overflow, the unit features an overflow panel so that the water can move back into the sump. In addition, water levels exiting the refugium chamber can be adjusted between 6-9 inches in depth via the adjustable water flow gate. Sophisticated acrylic construction also provides dosing, probe and wire holders which are conveniently organized by the built in fastener. Suitable for tanks up to 400 gallons.