by Wendy Connick

Created on: June 02, 2008

A refugium is a separate tank, sharing water with your main tank, that provides a safe place for plants and animals which would not be able to survive in the main aquarium. You can use a refugium as a holding tank for your live food, for example, or for creatures that are particularly vulnerable to predation. It also assists with filtration by providing a home for creatures that devour excess nutrients and undesirable chemicals.

To start, you'll need a minimum 10-gallon tank to hold your refugium and the larger, the tank is, the better. Ideally, it should reside between the main aquarium and the sump, as close to the main tank as possible; that way, you won't even need a separate pump. If you're using the refugium to store live food animals such as copepods, you can direct the refugium's overflow into your sump's final chamber, and your live food will be skimmed into the main aquarium for your fish's eating pleasure.

If you intend to stock your refugium with macroalgae, you'll need to provide a light source for them. Some experts believe that running your refugium and your main tank on opposite light-dark cycles helps to stabilize the whole system. Since plants only convert carbon dioxide into oxygen during light periods, alternating the periods in your two tanks keeps the oxygen/carbon dioxide balance fairly level.

You'll want a base of sand in your refugium at least a couple of inches deep, more if possible. A deep bed holds more nutrient-devouring microorganisms, and is less likely to be disturbed by water currents. You can get the life cycle up and running sooner by using live sand sand that is already inhabited by helpful microorganisms. You can also toss in as much live rock as you require for aesthetic purposes.

Macroalgae can help your aquarium system by eating the nutrients that would otherwise go to feed less desirable forms of algae. You can often order live rock with one or more macroalgae already attached. Caulerpa is perhaps the most commonly used macroalgae for saltwater tanks, since it is both easy to grow and removes harmful chemicals, toxins, and even heavy metals from the water. In fact, caulerpa is so easy to grow that it's been declared an invasive species in several areas. As a result, only certain species of caulerpa are available for aquarists, and you will need to trim them regularly caulerpas can expand at a rate of up to three inches a day.

Now that your refugium is properly equipped, you can sit back and enjoy the benefits of a natural filtering system!

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