DIY Refugium Sump

A refugium is an area of a saltwater tank that has been set aside from the main aquarium. Refugiums generally are used to give the creatures inside protection from the creatures outside. These smaller creatures may not be part of the design of the aquarium, but they almost always play an important role. Refugiums can be used to raise feeder organisms, algae or young fish, and they also can be used to increase the tank's water capacity and filtering system.

  1. Refugium Sump

    • A sump-based refugium is a separate tank that is placed below the aquarium. In this position, the refugium becomes part of the tank's filtration system, which consists of a pump, submersible heater, protein skimmer and filter sock. The refugium sump is connected to the main tank by two pipes--one to pump water into the tank and one to pull water out of the tank. This type of refugium is considered a "work" tank because it becomes part of the filtration system. This is where the pumping action takes place.

    Attaching a Refugium Sump

    • The sump pipes to the main tank can exist in one of two forms. For the first form, drill a hole in the side of the main tank and run a drain tube from that hole to the refugium sump. For the second form, use an overflow siphon on the main tank, and attach it to the tube running down to the refugium sump. Inside the refugium, you need a pump that returns water to the main tank at a rate of speed that's consistent with the drain or siphon. (The water level in the refugium always should be level.) Place a valve in the "return" tube, after the pump, to regulate the flow of water.

    Refugium Sump Pros

    • Even as part of the filtration system, your refugium sump can act as a separate tank for small organisms. Use it to breed and maintain feeders, such as copepods, or as a holding tank for young fish you've hatched. You also can use it to hold aggressive fish until they settle or new fish while they adjust to water temperature and salinity.

      Place a deep layer of sand (about 6 inches) in your refugium to further filter the water. The sand grows bacteria, which helps remove nitrates. Grow algae in your refugium to oxygenate the water. Plants in a refugium instead of a main tank keep the main tank clean while still giving your marine environment the benefit of plants' filtration.

      Finally, the sump refugium gives you a place to hide the tubes and machinery of your tank's filtration system.