Should You Use Sand In A Refugium? Pros And Cons

A refugium is an essential part of a saltwater aquarium and many aquarists choose to add one to their system. This is a separate, smaller tank that flows into the main aquarium. There are so many benefits of keeping a refugium which includes providing more surface area for beneficial bacteria to grow and populate.

It’s also incredibly helpful when it comes to cultivating plants, algae, or smaller creatures that may not be able to grow and reproduce as well in the main aquarium. These refugium inhabitants are often excellent at cleaning up pest algae or reducing harmful chemicals in the water, and they can also sometimes be used to feed the inhabitants of the main aquarium.

It is a very effective and natural way to lower nitrate and phosphate levels by removing nutrients from the system.

Refugiums are mainly set up to remove nutrients and provide extra filtration. If you decide to use sand in your refugium, there are some pros and cons that you need to consider. 


Should you use sand in a refugium? Pros and cons

 When you are setting up a refugium, you will have 2 options with respect to substrate use. You can choose to go bare bottom or use a substrate like sand. 

There are many advantages to using sand.


Deep Sand Beds


Miracle Mud is a popular choice! Click the image to check it out on Marine Depot.


When setting up a larger refugium, what substrate to use is an important question. Many aquarium keepers prefer deep sand in saltwater refugiums. These sand beds are usually between six and eight inches deep, although some aquarists feel that four or five inches of sand is adequate. This sand bed can serve several purposes.

It can be a place for small creatures to dig into or sift through. Different types of algae can also take root in the sand. Some algae can be an excellent meal for different types of fish, snails, shrimp, or crabs, and small amounts can flow from the refugium into the main aquarium.  It can also be an area to root plants like mangroves.



In addition, sand also often contains vital elements or minerals, which will give the main aquarium a boost.

Some people will use a deep sand bed (around 6” deep) for a place to grow bacteria and remove nitrates. When sand is deep enough that it doesn’t shift too much, there will be pockets where oxygen can’t reach.

In these sections, nitrates will be converted into gas by bacteria, and this gas will rise to the surface as a bubble. When the bubble bursts, the nitrates disappear, leaving the refugium and main aquarium much healthier.

sand in a saltwater refugium


The cons of using sand in a refugium are over time detritus and waste will collect on the sand causing an increase in nitrates and poor water quality. A huge concern would be releasing dead or decaying materials that are trapped in the sand back into the tank. The key to maintaining a proper deep sand bed in a refugium is performing regular maintenance to remove excess detritus.

Sand will occasionally need to be thoroughly cleaned or even replaced. This can be a very daunting project and may require removing everything else in the refugium.

Sand for Aesthetic Purposes

Although sand in saltwater refugiums can have many benefits, some people simply prefer to add sand because it creates a more natural appearance. In this case, the sand layer can be between one and two inches deep.

This thinner layer of sand won’t remove nitrates like a deep sand bed, but it can offer a place to root some plants and will be a shelter for certain types of copepods. This is also a good option for smaller refugiums that can’t support a large amount of sand required for a deep bed.

In addition, a thinner sand bed is often easier to clean and will generally require a bit less maintenance, although it will still need to be vacuumed often. 


Marine Depot Aquarium Supplies

Bare bottom refugiums

Although sand is often a good choice for a number of reasons, including a more natural appearance, many aquarium keepers prefer to stick to a bare bottom. Sand can sometimes cause as many problems as it solves.

For example, waste can often gather in the sand, and it can be quite a time consuming and difficult to clean up. This waste in turn creates nitrates, which can be very harmful to both the refugium and the main aquarium. A buildup of waste and nitrates can be deadly for an aquarium.

This, in turn, means that sand will require more maintenance than a bare bottom, which can be easily vacuumed or even wiped down. Aquarium keepers who are considering sand may also need to use more powerful filters in order to maintain a healthy refugium.

Utilizing a bare bottom, however, means that plants will need to either float or be rooted to other décor, such as live rocks. In addition, some copepods may not thrive, as they won’t have sand to sift through or bury into.


Miracle mud refugiums

Choosing the Right Substrate

Whether sand or a bare bottom is the correct option for a refugium depends largely on what purpose the refugium will serve. Refugiums that will be used to increase beneficial bacteria levels or grow smaller food sources such as macroalgae may not need a substrate at all.

However, if an aquarium keeper is looking to cultivate copepods, worms, or certain plants, a deep sand bed may be a better, healthier option.

Aquarists can also use a blend of substrates, such as sand and live rock pieces, to create a more natural environment and pleasant appearance in the refugium. You can use any marine aquarium sand that would normally go in a saltwater tank or give the Miracle Mud a try