How to Set Up a Refugium

Today, we’ll look at the advantages of refugiums and how to build one up in your reef tank. A refugium is a remote place that preserves and supports a wildlife population in biological terms. This theory underpins a reef refugium, which is designed to help your reef tank. The purpose of a reef refugium is to create a separate environment for the production of macroalgae, plankton, and biological denitrification from the main aquarium.

This is how it goes. Phosphate and nitrate are removed by macroalgae, lowering hazardous nutrient levels. Macroalgae can attach itself to pieces of rock rubble. Through the natural denitrification process, bacteria in the rubble will eliminate nitrates. Arthropods, copepods, and other microorganisms that corals and fish love to eat are reared in refugiums.

Many reef keepers used to believe that a refugium needed to be at least as big as the main aquarium to be effective. These massive refugias were entirely self-built, necessitating glass drilling and meticulous design. They also took up a lot of room. Today, we have the luxury of having ready-make refugiums develope exclusively for reef aquariums. For placement under your tank, there are in-tank, hang-on, and integrated sump alternatives.

The first step on your journey to refugium excellence is determining which type is best for your tank. Let’s have a look at a couple of the most popular options on the market. The CPR CITR 2 in-tank refugium does not require a water pump.

Suction cups secure the flow-through acrylic design inside the tank or sump. All you need is some light, macroalgae, rubble, and possibly some sand to create a refugium. The CUBE Nano Refugium from Eshopps contains a chamber for algae and rock, as well as a protein skimmer.

Simply connect it to the main tank, add a return pump, and a small LED light to complete the setup. A trigger system sump combines a refugium region and provides lots of extra room for a protein skimmer, filter socks, and other equipment if you have the space. This is a true under-the-tank, all-in-one solution. Some all-in-one reef aquariums contain enough space in the filter compartments to include a refugium. Filter sponges can be replace with sand and macroalgae.

A hang-on refugium, such as the AquaMaxx HOB-R, is another option. The AquaMaxx HOB-R is an ideal solution for existing aquariums with limited space beneath the tank for equipment. The unit attaches to the back or side of your aquarium with a small pump that circulates water through the refugium. After you’ve decided on the type of refuge, here are some advanced tips to help your ‘fuge work at its best.

Select the appropriate macroalgae.

Chaetomorpha algae has proven to be extremely beneficial to many reefers. It grows quickly, absorbs nutrients, is easy to harvest, and provides an excellent environment for microfauna to flourish and reproduce. Halymenia, commonly known as dragon’s breath algae, is a top performer that grows quickly and would thrive in a refugium. Another common refugium resident is Caulerpa. It has some negative side effects, despite its popularity.


Caulerpa is a resilient and prolific plant that is ideal for refugiums. However, that means it can readily suffocate rival algae for light and space. Caulerpa can also spread spores throughout your aquarium, and when it dies while spreading spores, the nutrients and poisons it has taken are release into the water. Because it’s a natural reproductive mechanism, many aquarists refer to this as “becoming sexual.”


As a result, your display aquarium may see a major influx of extremely hardy caulerpa, which may crowd out your corals for space.

It will also degrade the quality of your water. Caulerpa known to manufacture and release poisons that protect algae from herbivorous animals in the wild. These poisons have linked to difficulties with thin corals, particularly SPS corals, in our tanks. Furthermore, many of the corals we keep are never find in the same area as caulerpa species in the wild, so why would you expect them to coexist in an aquarium? The takeaway here is to be wary of caulerpa.

Light is require for macroalgae to grow. The primary aquarium lamp usually provides enough light for in-tank and hang-on refugiums. Refugiums that are positione far away or under the tank, on the other hand, require a light source. For this use, a basic full spectrum LED fixture is ideal, and we have a number of outstanding alternatives in store. Online, you can also find a variety of DIY ideas.

The truth is that macroalgae can grow in any full spectrum light source, yet some lights are clearly superior than others. Because science has demonstrated that certain color spectrums encourage a better rate of photosynthesis inside macroalgae, the spectrum of light utilized for refugiums has become a hot topic recently. As a result, an increasing number of companies are releasing LED lights with a strong red and blue color spectrum to encourage algae growth.


A more advanced ‘fuge strategy is to light the refugium on the opposite side of your display tank’s lighting schedule.

The goal is to achieve a balance between oxygen production and CO2 elimination. Photosynthesis stops inside your aquarium at night, and the corals stop taking in CO2. As a result, more CO2 dissolved in your aquarium water, which lowers the pH level. By running your refugium at night, the algae within will continue to absorb CO2 and assist lessen the natural pH swings that occur throughout the night in your tank.

It’s crucial to periodically harvest a piece of your macroalgae by removing it from your refugium as it grows. Nutrients held in algae cells may seep out, particularly if the algae begins to die. Harvesting guarantees that the nutrients in the tank totally eliminated. This also allows for the growth of new macroalgae, which can continue to consume unwanted nutrients. Here’s another suggestion.

When harvesting macroalgae from a refugium, it’s usual practice to gently shake the removed clump of algae in the aquarium water.

The pods and other beneficial creatures will released back into the refugium or directly into your display for your fish to eat. Seeding your refugium with copepods is a good idea, especially for freshly formed aquariums that don’t have a well-established, stable pod population. Using Miracle Mud or Fiji Mud as a refugium substrate has several extra advantages. However, a refugium is not required to gain the benefits.

For the sake of keeping things clean, I personally do not utilize substrate in a refugium.

I usually use a small clump of chaetomorpha with a few bits of rubble rock. In general, the flow rate through a refugium is somewhat slow. You don’t want to be pushing water through it since it will disrupt some of the beneficial activities that are taking place inside your refugium. High flow will also disperse substrate or algae fragments throughout your display.

It’s never been easier to set up a refugium, and the benefits are substantial. Your reef tank will benefit from less nuisance algae, lower nitrates and phosphates, and plenty of live meals for your fish and corals, regardless of the type of ‘fuge you set up. Thank you for spending today learning about refugiums.