Refugium: 17 Things You Should Know (For Beginners)

A refugium is an interesting piece of equipment that offers lots of improvements to your aquarium.

Some tank owners, especially those that just started their tank journeys, have never heard of this before and it’s additional perks.

If you are interested in setting up a refugium, it is necessary to familiarize yourself with it first.

What Is A Refugium Tank?

A refugium tank is a detached space that shares a similar water supply with your aquarium and serves as a shelter for thriving aquatic organisms.

A refugium tank is basically an auxiliary box from your main display aquarium that offers great benefits and multiple uses.

It can be used with different tanks – may it be brackish, cold water, fresh water, saltwater, or even tropical aquariums. It also has three types: in-tank refugium, hang-on-the-back refugium, and sump/separate tank refugium.

A refugium tank is a sanctuary that provides a safe environment for different organisms that cannot fully flourish in the main aquarium. They need to breed as they are the live food of fish and corals.

Algae can also be grown in a refugium which helps in the maintenance of water as they extract nitrates and waste.

Is Refugium Necessary?

No, a refugium is not necessary. Yet, having one will bring lots of benefits to your tank.

A refugium is not really needed in your aquarium. You can definitely set up a tank without it and not fret about the safety of your aquatic inhabitants.

It is simply a piece of additional equipment to boost your tank’s overall biodiversity. Having one will surely be beneficial but you can assuredly have a suitable aquarium for your aquatic friends without it.

Is A Refugium Worth It?

Yes, a refugium is worthy. It is an effective device to grow beneficial creatures to improve the filtration of your main tank.

A refugium tank can be compared to a sanctuary that provides a calm and safe setting for different organisms (algae, corals, live sponges, natural fish food) that cannot fully flourish in the main aquarium. They need refuge as they are usually facing threats of being bullied and even eaten.

These organisms are propitious when it comes to your tank’s maintenance, likewise in improving the biological filter system.

A refugium tank is sharing water with the major tank, thus, enabling it to do filtration also as it may serve as an overflow tank.

You can also consider having this additional box if the additional beneficial creatures that you want to have will unpleasantly affect the aesthetic view of your main aquarium.

What Is The Difference Between A Sump And A Refugium?

The difference between a sump and a refugium is their primary function. A sump acts as a storage facility to consolidate equipment while a refugium is utilized as a haven in improving various organisms’ growth and proliferation.

If you are a new hobbyist, you may find a sump and a refugium to be comparable. You may think that you can use them interchangeably given that they share the same advantages.

Though they indeed share some similar benefits, they are two different pieces of equipment that have different major functions in your tank. Some would prefer having only one of these two, but installing both will help you achieve an optimal system of filtration.

A sump is a supplementary tank housing various filtration and monitoring aquatic devices like filters, heaters, and skimmers with all their pipes and wires.

It is conveniently allowing you to customize the organization of these sets of hardware in just one area. It helps in maintaining the right setup for your main tank in the most clutter-free way.

Meanwhile, a refugium is primarily used in housing different plants such as algae that helps in keeping the water safe. Likewise, it provides a safe place for live food creatures like copepods that cannot survive in the main tank.

When Should I Add A Refugium To My Reef Tank?

You should add a refugium in your reef tank once its system cycling is finished.

A refugium is needed once the nitrates spike. There are not enough nitrates yet while you do the cycling in your tank so you just need to simply wait until the perks of a refugium are needed.

Adding a refugium after the cycle will enable it to only extract excess nitrates, thus, retaining the suitable nitrates that your reefs need. This is critical to note since a deficiency in nitrates will adversely affect the corals because of insufficient nutrients.

Do You Clean A Refugium?

Yes, you should clean a refugium once in a while depending on its condition.

Cleaning a refugium depends on the preferences of tank owners and its sanitary condition.

Some do not do a major cleaning, because for them a refugium is helping in the major tank maintenance, thus, it can also stay clean by itself. Simple care is enough such as moving away tall algae from the front panel for a clear view.

Yet, it would be better to do tank maintenance, probably once a month or every three months, to make sure the refugium tank will effectively operate to attain its maximum benefits.

Regular cleaning of skimmer and return pumps is definitely essential. You can also remove some hair algae if you want to have a fresh refugium every after cleaning when it comes to build-up.

How Big Of A Refugium Do I Need?

The refugium that you need can be of any size depending on the size of your aquarium. As recommended, your refugium should be 20% of your tank’s size.

Your refugium should be big enough to accommodate all the organisms and other things that you want to house in it. Following the advised size based on the capacity of your aquarium will make sure that the refugium will work effectively based on your expected benefits from it.

How Much Chaeto In A Refugium?

You can start with any amount of chaeto in a refugium.

There is no standard amount of chaeto needed in a refugium. You can start by adding a small handful and it will grow based on the measure of nutrients in your system.

You just need to do regular harvesting so there will be ample space for growing new chaeto.

Can A Refugium Be Too Big?

Yes, a refugium can be too big. You can freely choose to have a bigger refugium so you can add more things to it and improve the filtration system of your main tank.

Although the recommended size of a refugium is 20% of your main tank, it would not cause harm if you go for an even bigger size.

The saying “the bigger, the better” can be applied with the case of a refugium. The larger it is, the more advantages you can get.

You might be surprised and thankful at the same time that you get a bigger refugium once you enjoy putting in a lot more beneficial organisms as time passes by.

Should I Put Sand In My Refugium?

You can put sand in your refugium, however, it is not necessary.

You have a lot of choices when it comes to the types of substrate to use in your refugium.

You can use sand, rocks, or rubbles of rocks. You can also consider Marine Pure block or Miracle Mud. If you don’t prefer any of these, you can simply leave the bottom of your refugium plain and uncovered.

Putting live sand is beneficial in promoting the growth of specific species of algae. However, some do not prefer having sand due to its advantages such as being high maintenance.

Do You Need A Refugium For A Fish Only Tank?

No. You need a refugium not only for fish tanks but for other types of aquariums as well.

With the advantages of a refugium tank, it would be beneficial not just for fish tanks. It can be used with different kinds of tanks such as brackish, cold water, freshwater, marine, or even tropical aquariums.

Can You Keep Copepods Without A Refugium?

Yes, you can keep copepods even without a refugium.

Having a refugium is highly beneficial for copepods to ensure they will successfully thrive and reproduce. Yet, it is not really needed as you can still secure the safety of these nutritious food sources using other methods.

You can put copepods together with other aquatic creatures but you must make sure you will provide effective protection for them. If not, they will not grow and multiply as your fish will surely eat all of them spontaneously.

One thing you can do to guard copepods is by growing algae as they can hold and hide on these organisms. Adding some debris piles can also give copepods a secured zone to hide them from predators.

What Do You Feed Copepods In A Refugium?

You can feed copepods with fish food and phytoplankton in a refugium.

Copepods are flexible organisms that can survive by consuming any kind of food that is available for them.

Aside from being nutritious food for fish and other creatures, they are also improving the sanitation of your aquarium by eating film algae, detritus, and even excess food.

You can feed copepods with meaty food that can easily dissolve such as fish food (pellets and flakes).

Another of their favorite foods is phytoplanktons that you can culture. You can find a lot of phytoplankton culturing kits in the market. You can also use live phytoplankton products like OceanMagik.

Do I Need A Protein Skimmer With A Refugium?

You do not necessarily need a protein skimmer with a refugium. You can just choose between the two or you can have both of them.

A protein skimmer and a refugium are helpful devices in maintaining the cleanliness of your tank. Having both of them will give truly amazing benefits to your tank as well as your aquatic pts.

Yet, if you are to choose only one, a skimmer is more recommended as it is providing a more stable performance when it comes to extracting excess nutrients and toxins.

Do I Need A Refugium For A Nano Reef?

You do not necessarily need a refugium for a nano reef, but you can get one if you want.

A nano reef is quite small that regular water changes will be enough for its maintenance.

As advised, the refugium should be 20% of the main tank. Thus, the refugium for a nano reef would be too little that it might not be really useful and not worthy to invest in.

Do You Need A Refugium For Copepods?

No, you do not need a refugium for copepods. They can still live in an aquarium together with other aquatic creatures.

A refugium definitely provides a safe place for copepods to develop and breed. But having one is not a necessity for copepods to flourish.

They can live together with various fish as long as they have a safe place to stay in the tank. For instance, growing algae will provide them an area to hide and grow as fish will not easily see them as they hang onto these algae.

What Is The Size Of Refugium For 125 Gallons?

The size of a refugium for 125 gallons is 25 gallons.

As recommended by experts, the size of your refugium should be at least 20% of your aquarium.

This dimension will provide a production refugium as it can hold more plants, creatures, and other things that will add more benefits to the main tank and its inhabitants.

Refugium Tanks

There are various kinds of refugium tanks in the market. Below are some of the most popular brands that you might consider.


Page, A. (2021, August 9). Refugium VS Sump: What’s The Difference? Tankarium.

PetMD Editorial. (2019, February 11). Five Reasons To Install A Refugium On Your Saltwater Aquarium. The Best Pet Health & Care Advice from Real Vets | PetMD.

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