Most Reef Aquariums will use this form of filtration. It is a highly adaptable piece of equipment which uses a seperate tank (normally fitted under your aquarium) where water flows via an overflow box, filtered through a set of emdia and then pumped back into the main tank.

A Sump is a little complex in that you need to have regulators in place to stop water spilling out of either the main tank or the sump. Normall this is in the form of a water llevel cut off switch in the sump, as when the water level drops (when the main tank's overflow box is blocked) the switch cuts off the power to the pump, thus preventing a sspill from the main tank.

Most tanks with a sump system have a drilled hole in the base. This is the easiest way of getting water from your main tank (gravity fed), however you can buy overflow boxes which attach to the side of the tank, and using a suction system feed the sump. Most modern overflow boxes retain their suction and in the event of a power cut they still feed water to the sump. (without this the main tank will overflow).

The sump is sometimes called a trickle filter because water "trickles" through pipes and into a trickle bar. This ensures the water is subjected to huge amounts of oxygen, which aids nitrifying bacterial growth. It is this method of oxygen enrichment that has made the sump popular, but its the sheer capacity for storage of equipment which has made a must have.

The large sponge removes large detritus from the water while the Bio Balls provide a high surface area for bacterial colonisation. The Fine Filter Sponge polishes the water, removing fine particles suspended within the liquid. The water is then returned via the pump into the tank. Not shown here is the capacity for the sump to hold all equipment normally seen in the display tank (such as heater, protein skimmer, filter, cooler etc) and its this that makes a sump unique.

Click here for Overflow Diagram