Refugiums are great because they provide a means to export waste and nutrients and also provide a safe haven for small, beneficial organisms to grow and reproduce. These small creatures, including copepods, amphipods and other ‘bugs’ which thrive in a refugium will help to devour leftover food and detritus. As some of these ‘bugs’ will inevitably make their way into the display tank, they will also help feed the animals in your reef tank and increase the biodiversity in your aquarium.

In this article we are going to set up an in-sump refugium, provide some helpful tips to make set-up hassle free, and show you how to get the most out of your refugium.

Since refugiums have become so popular, many of the sumps we carry are now designed with compartments ready for a refugium. Both the Precision Marine and Trigger Systems sumps are perfect options and offer various sizes to fit just about any tank.

See, for example, the Trigger Systems Emerald sumps. Notice how a baffle separates the first chamber from the second. This second chamber is an ideal place for a refugium. The baffles ensure gentle water flow through the refugium and will keep all of the sand, rocks, and other things inside your refugium where they belong- away from your return pump in the third chamber.

The first chamber is reserved for your protein skimmer and other filtration equipment, such as media reactors. It is always best to have your skimmer receive ‘dirty’ water from the aquarium before it is filtered by the refugium. This will increase the effectiveness of the skimmer and prevent those tiny beneficial organisms growing in your refugium from getting chopped up or removed by your skimmer.

In order to set-up your refugium, you will need: a light, substrate, some rubble rock and whatever you plan to grow in the refugium.

Chaetomorpha and Caulerpa are the most popular macro algae for refugiums because they are easy to grow, which makes them very effective for controlling nutrients and provides a great habitat for copepods and amphipods. Mangroves are also a great option but do have some additional care requirements so be sure you are willing to put forth the extra effort and have the space required to grow a Mangrove.

For substrate, sand is perfectly suitable but refugium mud is the best choice. We offer a few different types of refugium muds including the popular Ecosystem Aquariums Miracle Mud, CaribSea Mineral Mud, and Walt Smith Fiji Mud. Refugium mud is extra beneficial because it helps restore trace elements and is the perfect size and texture for micro-organisms to burrow and reproduce. Additionally, the fine grain size and dense nature of the mud creates nitrate-reducing anaerobic zones with just 1-2 inches of depth. With regular sand, it will take 4 inches or more to create an effective anaerobic zone.

Rubble rock is used to anchor Caulerpa. You can use a small piece of fishing line or thread to attach it. Chaetomorpha usually tumbles freely in the refugium. The porousness of the rock also provides space for the ‘pods’ to reproduce. Macro-algae is grown in a refugium because it will absorb nitrates and phosphates from your aquarium water and help prevent the spread of nuisance algae in your display aquarium.

A full spectrum light in the 6500-10,000K color range works best. We are using the WavePoint Micro Sun, which has the right spectrum and power at a great price. The Tunze Full Spectrum Submersible LED is another great option because it is waterproof and comes with a versatile magnetic mount.

Many hobbyists run the refugium light at night, opposite of the display aquarium's photo period, because doing so helps reduce large pH drops when the lights are out in your main display. This is called reverse daylight photosynthesis (RDP).

Once everything is set, you can start to add water. Refugium mud can cloud your water pretty bad but if the water is added slowly you can reduce the effects. Once it is filled with water, let it settle before turning on your pumps. It is also a good idea to fish out any floating debris with a net prior to turning on your pumps.

As the refugium becomes established, macro-algae will start to grow quickly. You will need to periodically harvest the overgrown macro-algae and remove it from your refugium. This is how the nitrate and phosphates are removed from your aquarium water.

Algagen offers a few different types of live ‘pods’ that can be added directly to your established refugium to help increase the biodiversity and seed the refugium with different species. Just give your refugium, and your tank for that matter, plenty of time to cycle before adding live copepods.

If you are looking to get a sump or install a refugium, Marine Depot has everything you need and our trained team of aquarium experts are happy to help. Just give us a call at 800-566-3474 or send an email to Until next time, take care and happy reefkeeping.