Some people are scared off by anti-refugium rhetoric, while others are deterred by the apparent complexity of plumbing required to add a refugium to an existing set-up. In reality, however, a refugium is neither confusing nor detrimental. In fact, a properly installed and maintained refugium should increase both the health and stability of your system, while, at the same time, opening up the opportunity to house species you previously could not keep.
At the basest level, a refugium is a refuge—hence the name. It is a place that will share water with your display tank, but it will not be disturbed by animals or excessive current velocity. The refugium is a place where live food sources (e.g. copepods) can thrive. With a deep sandbed, the refugium will help export nutrients from the overall system without the risk of being disturbed and releasing toxic levels of nutrients into the water column.
For your refugium, like the display tank, you should use the largest tank you can. Not only does this provide more habitat for macroalgae, other marine plants (like seagrasses or mangroves) and beneficial invertebrates, a larger refugium also adds more water to the overall system and, in turn, helps to further stabilize the display tank. Many people, however, are limited by space and can have a refugium no larger than 10 gallons.
A ten-gallon refugium with a deep sandbed of at least four to six inches can be ideal for many small systems. It is a good idea to use a marine mud product or live sand for your substrate, as this will jumpstart your refugium. Ideally, the refugium will be supplied with water by splitting the display tank’s drain using a ball valve on the refugium side of the split so you can regulate the flow allowing most of the water to go directly to the sump. Once the refugium is up and running, you can adjust the flow so there is just enough current in the refugium to keep the water from stagnating, but not enough to disturb the sandbed.
The refugium should be located between the main display tank and the sump so an additional pump is not necessary. If you locate the refugium on a shelf under the display tank and above the sump, for example, the water can flow from the display tank into the refugium and from the refugium into the sump using gravity alone. Ideally, the refugium’s overflow will be directed to the last chamber of the sump (after any skimming or mechanical filtration) so that it can be pumped directly back into the display tank via the sump’s return. In this way, copepods can flow into the main tank and provide live food for species such as mandarin gobies and anthias that depend on a constant source of live food.
The refugium will need a light in order to grow macroalgae. Some aquarists like to run this light on an opposite cycle as the display tank’s lights so that the system’s pH remains more stable.
Once the refugium is set-up, add some macroalgae and maybe even some other marine plants. You may also consider adding certain beneficial invertebrates that will not eat the vegetation you are attempting to grow.
Once this simple refugium is established, you will begin to reap the rewards of a more balanced system with additional biological filtering capacity and a perpetual source of live food. Maintenance includes tending to the vegetation (trimming, removing dead leaves, etc.), replacing the bulb and regularly checking the inflow and overflow just as you would on either your display tank or sump.
Ret Talbot - Ret Talbot joined Suite 101 in December 2007, and he is now the feature writer for saltwater fish—a topic in which he is both ...
