How to Make a Refugium for Saltwater Aquarium

  • By:

    Alina Andreeva
    Alina Andreeva

    Author: Alina Andreeva

    Alina A. is a professional writer, editor, and pet-lover. She has published over 30 articles on how to care for pets properly. Alina has been writing articles for 3 years, so she has considerable experience in this niche. Her natural curiosity helps her to expand her knowledge and learn new pet care life hacks, which will make your life much easier.

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  • Updated on: 10/20/2020

One of the biggest problems in keeping fish is choosing what to include in your tank. There are so many boxes to tick and questions to answer. Can the fish live in saltwater, or does it prefer freshwater? Can you purchase more than one of the same fish, or do they act aggressively towards their own species? Is your tank big enough for them? How many fish can you fit in your container? Planning your aquarium is a delicate business, as you want to achieve a certain equilibrium in which every fish is happy and healthy. Unfortunately, some more aggressive fish are known to attack the more delicate within the tank. Upstep the refugium.

refugium for a saltwater aquarium@davit85 / FreePik

What is a Refugium for Saltwater Tanks?

Refugium is a ‘refuge” that provides a separate tank for the more docile and at-risk species, keeping them safe from aggressive predators. Delicate species, such as corals and anemones, should not be held within the same tank as those who attack them.

What does a Refugium do?

Refugium allows you to connect your main tank and smaller refuge tank within the same display while keeping certain species isolated from others. These tanks can be held side by side, with the same water filtration systems. In truth, only as an extra layer of class prevents them from being the same tank.

A refugium is made to be seen, not hidden away like a reverse photosynthesis device. It is merely a quiet and safe place for copepods, seahorses, shrimpers, and more to swim, free of danger.

What to put in my Saltwater Refugium?


In terms of species, you should put any fish that would not survive and thrive within your standard tank into the refugium. There is space for them, and none of the species in the refugium are aggressive towards each other, it is doing its job. If you are looking for examples of particular species, then seahorses, shrimp, copepods, snails, corals, crabs, and more can be added to your refugium.

Sand Bed and Rock

However, a refugium is about more than the fish and creatures you put into it. This is also a chance to create an aesthetically-pleasing sub-section to your display tank, as primary filtration is not an issue with a refugium. Many people like to add a sand bed, around one or two inches deep, to their refugium. You can also add a few pieces of rock to this sand bed. This sand bed will make the tank look nice, but it will also provide a home for beneficial worms and other sifters. Creatures like crabs are also used to having such a base to walk around on.

Plants and decorations

You can also feel free to add plants and decorations, as long as they suit the species you are adding to the refugium.

READ MORE: Getting Rid of Brown Algae

How to make a Refugium?

The most challenging part of establishing a refugium is the actual creation. We recommend using a second smaller tank, although a cheaper way to achieve a similar result is to section off a portion of your existing tub.

First of all, ensure that you turn any pump off. Take your sand or mud and fill the refugium up to around one or two inches. Make a judgment call based on how big/tall the refugium is. You can then add your rocks or any other media of your choice. Remember to rinse them out and clean them before adding them. You can then add some macroalgae, although ensure that it is fixed to the bottom of the tank with string, a rock, or a rubber band.

Otherwise, you risk it clogging the pump/filter. At this point, you can pour your chosen species into the tank and allow them to explore their new home. You should give the various creatures some food reasonably early on to get them used to be fed within new surroundings.

Make sure that you now let the refugium settle before turning the pump back on. This ensures that all the small bacteria, crustaceans, and co can bed themselves into the sand, preventing them from being sucked away. You should then add a light above your refugium tank, as you would a typical aquarium. Make sure to harvest the macroalgae every two to four weeks to prevent overgrowth.

READ MORE: How to Clean a Freshwater Tank

Refugium Diagram

refugium for saltwater aquarium guide

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