DIY Saltwater Refugium

A saltwater refugium is, quite simply, a refuge from the main aquarium for animals and plants. It is physically separated from the main tank, but it does share the water with the main tank. A refugium is used by aquarists for a variety of purposes including to quarantine new or bothersome fish; to isolate access into the tank itself such as for water or equipment changes; to smooth the affects of diurnal rhythms; to improve temperature stability; to increase system volume; or to grow macro algae.

  1. Primary Objectives

    • There are many opinions about how best to implement a saltwater refugium. The place to start is to identify your primary objectives for having a refugium. Your purpose will impact all future decisions. For example, if your primary purpose is to quarantine new fish, then you will create a refugium just large enough to accommodate some live rock or coral in addition to the fish itself. On the other hand, if your purpose is to increase system volume, you may need a much larger refugium.

    Budget

    • Budget is the second major factor you need to consider when planning your refugium. In many ways, a refugium is a small, but complete, aquarium system; it requires water flow, filtration and light. Most aquarium components have options that are less expensive and options that are more expensive. For example, a small, clear acrylic sump can provide an inexpensive and self-contained backpack-style refugium. Knowing your budget will help you make the best trade-offs based on your primary objectives.

    Size and Placement

    • With your primary purpose and budget firmly in mind, you can begin to make decisions and craft together the components of your refugium. Size and placement are important factors at this point. An easy and unobtrusive location for a refugium is directly in the sump. This strategy may require minimal modifications to your sump. You can also locate the refugium next to or above the main aquarium display. This up-top display has the advantage that good organisms can naturally flow back into the main tank, as opposed to the in-sump method in which the sump will likely destroy any overflowed organisms. The disadvantage to the backpack or side-by-side display is that it is visible.

    Lighting

    • The type of lights you apply to your refugium will be governed by the location and what kinds of organisms or livestock you will put into the refugium. For example, you could not use a pendant light over the top of an in-sump refugium. Regardless of the type of lights, you will need to set up a timer mechanism that is separate from the main tank. This separate timer allows you to run the night/day patterns opposite of each other: when it is day in the main tank, it should be night in the refugium. The advantage of alternating the day/night cycles is it smooths some of the chemical changes inherently caused by day/night cycles.

    Plumbing

    • Plumbing is perhaps the trickiest part of creating your refugium. Establishing appropriate water flow and protecting against overflow in case of a power outage are primary considerations.