DIY Plans for an Above Tank Refugium

A refugium is an area of a saltwater tank that has been set aside from the main aquarium. Refugiums are generally 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 almost always play an important role. Refugiums can be used to raise feeder organisms, algae or young fish, and can also be used to increase the tank's water capacity and filtering system. An above-tank refugium is best used for raising feeder organisms like plankton and copepods.

  1. Attachment

    • An above-tank refugium is a separate tank placed above the aquarium. In this position, the refugium becomes another step in the filtration system, which consists of a pump, submersible heater, protein skimmer and filter sock. Connect the above-tank refugium to the main tank in two places--one to pump water up to the refugium from the main tank, and one to return the water back to the main tank. This type of refugium works with gravity to return water to the main tank after it's been through the refugium, instead of using the strength of the pump.

    Mechanism

    • An above-tank refugium pulls water out of the main tank to keep the refugium's water supply fresh. Attach a hose to the main tank's water pump, and run it up to the refugium. Water should be returned to the main tank from the refugium in one of two ways: either by an overflow box, in which water overflows from the refugium into the main tank, or by another pipe, in which water runs down the pipe from the refugium to the main tank. The water flow rate should be even and the water level in the refugium should always be level. To control the flow rate, place a valve in the "entry" tube, after the pump, to regulate how quickly the water flows into the refugium. If you're using an overflow box, you should also be able to regulate how much water is being returned to the main tank.

    Uses

    • 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 like copepods and plankton. The refugium will give these small feeders a place to breed and lay eggs without danger of being eaten. The constant flow rate means there will be a constant gravity-controlled supply of food entering your main tank.

      You can also use your refugium as a holding tank for larger fish that need time to settle into your tank's aquatic conditions. Always make sure the fish are large enough to withstand the overflow of your refugium. Above-tank refugiums aren't recommended for small fish, as they will get caught in the overflow and be returned to the main tank.

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