Sump in Aquariums

A sump is a separate tank placed behind or below the main aquarium.  The function of the sump is to house the equipment which may be unsightly.  Equipments such as filters, sterilizers, heaters and chillers can affect the aesthetics of the tank.

Hence, in large tanks, a separate tank which is connected to the main tank serves as the sump.

Reef Tanks always have an sump as part of their design.