A refugium refers to a smaller aquarium that is connected to your saltwater aquarium and cycles the water in and out of the main tank. They are often placed underneath the main tank and in a sump. 

Different Types of Refugiums

Sumps house all your equipment and contain tanks that drain and maintain the water of your aquarium. This means there is more water in your aquarium and therefore it is easier to maintain. The sump will be connected to the main display tank via an overflow. This water will flow through the different chambers of your sump and then back into your main tank. Your refugium will be one of these tanks in your sump. 

You can also have an in-tank refugium which is a small container in the aquarium that lets the water in but keeps the marine life out. This means you can safely grow plants or smaller creatures without the threat from predators. However, this does not add water volume to your tank which is really helpful in keeping the water healthy and stable. 

Some hobbyists also choose to hang their refugium on the side of the main tank and cycle the water in and out. This helps with the water flow but it does mean your refugium can’t be too big! 

Whichever type of refugium you add to your saltwater aquarium is up to you, your needs, and your budget. Adding a sump into your saltwater aquarium is a great addition, but it is costly. But, thankfully there are other options when it comes to refugiums, such as in-tank or hang-off. 

Why Use A Refugium?

The refugium acts as a natural filter to the water in your aquarium. They create more water changes in the tank and keep on top of the levels of nitrate and phosphorus. They aid in stabilizing the water, maintaining a healthy amount of oxygen. When used as a part of a sump, refugiums also mean that you can add trace elements into your aquarium when necessary. 

The main reason why you would want to use a refugium is because of the life you can maintain in the mini aquarium. It creates a home for any algae that you don’t want in your main tank. It also can absorb waste that you have in your aquarium as the algae will feed off any debris from your fish. 

Its other main use is for the creation of a home for smaller marine life that aid the ecosystem of the aquarium, but are in danger of being eaten by bigger creatures in the main tank! You can put your amphipods and copepods into the refugium to feed off the debris that will gather in the tank. 

If you have corals, anemones, and smaller fish that will be harmed by predators in your main aquarium, the refugium acts as a way to protect these creatures but also allowing them to enjoy the ecosystem. 

You can also grow algae and other plants in the refugium that you are wanting to harvest and feed to the marine life in your main aquarium. If your refugium is in a sump, you can provide different lighting that the plants might need to flourish. Providing different lighting also means that you can add oxygen to the water during nighttime hours. This is a great way to keep the pH levels stable. 

As you can see, there are so many great reasons to add a refugium to your tank, but what exactly shall you put in it?

What to Put in Your Refugium?

The first decision you have to make in regards to your refugium is what kind of substrate you are wanting to use. Sand or mud are both great to use in your refugium, or you could opt for rock. You could also leave the bottom of the tank bare. It really depends on what you are used to and happy using, and what kind of stuff you are wanting to add to your refugium!

You probably want to add macroalgae into your refugium. They are great as they act as a filter for your water and remove things like nitrates. They also take these things from the microalgae, and therefore don’t allow the microalgae to grow!

They can also be harvest and used to feed the marine life in your aquarium. A lot of fish and crustaceans love macroalgae, and keeping them in the refugium means you can keep the plants healthy and feed them to your creatures when it is necessary. 

You might also want to put in copepods and amphipods into your refugium in order to keep your aquarium clean and free of debris! Because they are safe in the refugium, they won’t get eaten by the bigger creatures who like to feed on them. Similarly, scavengers can be put in the refugium to keep on top of the cleaning whilst being protected from predators. Snails, crabs, and slugs will all do well in the refugium. 

Refugium Maintainance Tips

In order for your refugium to be successful, you need it to be well lit and on a timer. It is advised for the lighting to come on when the lighting on the main aquarium is turned off, as it keeps the water levels stable. Find the best lighting for what you are wanting to put in your refugium to ensure your marine life has the best chance to thrive!

Remember to harvest the macroalgae when necessary, and feed the tiny crustaceans. You should also keep an eye out on the levels of copepods and amphipods! Add more if you need to. 

Final Thoughts

If you are looking to up your saltwater aquarium game, go and add a refugium! They provide so much help in keeping your marine life happy, from keeping the water clean to growing tasty food for them!