If you are new to the saltwater/reef aquarium hobby, you may or may not have heard the term "refugium". Chances are that you have heard of a refugium since you are here. However, that term can be confusing, especially because it means different things for different hobbyists. We will go over what the term refugium can refer to. Whatever your understanding of a refugium is, you are probably wondering if you need one in your aquarium. We will discuss that as well. Putting on your reefing gloves, and let's dive in (pun intended).
You don't need anything in your aquarium
Before you get rid of all your equipment, let me explain what I mean by "you don't need anything". You certainly need some components to run a reef aquarium, but there is no one specific thing you need other than the actual aquarium maybe. Yes, you do need some sort of filtration and some sort of light and some sort of way to make flow, but there is no one way to do any of those things. There is not one type of equipment or component that every single aquarium has. For example, some aquarium use sumps for filtration while others rely on hang on the back equipment. Some aquariums implement a filtration section that is the back of the aquarium. Although LED lights are most popular, T5 lighting and even metal halides are still an option. Some hobbyists even have beautiful sunlit reef aquariums. One hobbyists might use filter socks while another might have a complete absence of mechanical filtration. Even though most aquariums have protein skimmers, there are a lot that don't. The point is, that very few if not any specific components are required to run a successful reef aquarium.
How hobbyists decide what they want to run on their aquarium is by determining what they want to do with their aquarium. Do you want to have corals? Do you want a mixed reef tank, softie tank, SPS tank, or an LPS tank? What kind of fish do you want to keep? What kind of colors do you like to see? Those are the type of things that determine what components you add to your tank. You also need to think about the maintenance you want to do. Most hobbyists are okay with doing a water change per month or biweekly, but most don't want to do more than that. That is why a lot of reef aquariums run protein skimmers, algae scrubbers, calcium reactors, etc. Most hobbyists also prefer vibrant corals, which is why a lot of aquariums use LED or T5 lighting instead of the sun. People don't use metal halides because they don't like the amount of heat produced and the amount of energy consumed. That doesn't mean you can't use metal halides. Before you do something to your aquarium or add some sort of equipment, you need to understand why. Don't do things just because it is what other hobbyists do.
What is a refugium?
Before we talk about why refugiums are used, let's establish what a refugium is. In its most basic form, a refugium is a place to grow organisms that you don't want to grow in the main display, can't grow in the main display, or organisms that need to have a protected population. It is generally agreed upon that if a "refugium" consists of just a floating ball of macroalgae, it is more of a macroalgae reactor. A refugium has multiple kinds of organisms living in it that serve multiple purposes. That is what a refugium is fundamentally.
Now, a lot of hobbyists only consider something a refugium if it is separate from the tank and the sump. These kinds of refugiums are usually connected with pumps and tubing. While these are certainly refugiums, they are not the only kind of refugium. Refugiums can generally take three shapes: whole separate tanks, a section in the sump, or a hang-on-the-back refugium. The most common are refugiums that take up a section in a sump. Some hobbyists don't consider these kinds of refugiums actual refugiums. However, they can certainly be refugiums. After all, the word does not matter as much as the function. If it functions the same as refugiums that are separates tanks, it is a refugium. Sump refugiums are by far the cheapest option if you already run a sump on your aquarium. The other two options require you to buy an additional container. Sump aquariums are probably not as effective as whole tank refugiums, but they are much easier to manage and beginner friendly. Although not as effective, sump refugiums still work great for a variety of different purposes.
Refugiums usually consist of some kind of substrate, rocks of some kind, macroalgae, and microcrustaceans. They are usually lit by a dedicated refugium light as well.
That is what a refugium is. It is a broad term that can refer to several different things that all generally do the same thing. Onto the purposes of a refugium.
Purpose of a refugium
So, why should you even consider adding a refugium? Refugiums are a very popular part of a reef tank and they have been for a while. The great thing about them is that they can serve many different purposes at once, and they are generally simple.
Arguably the most common use for a refugium is to grow macroalgae. Hobbyists grow macroalgae to compete with pest algae in the display. Macroalgae can do this by consuming nutrients that would otherwise be consumed by pest algae. Macroalgae can also clean the water of impurities and toxins. Certain kinds of macroalgae can also be fed to herbivore fish such as tangs. There are so many uses for it. Remember, a refugium isn't really a refugium if it is just macroalgae. This is because something that just grows macroalgae is a macroalgae reactor or scrubber.
That leads us to the next purpose of a refugium: copepods. Like macroalgae, copepods themselves serve a lot of purposes. Concerning macroalgae, copepods can help keep the macroalgae clean of detritus and pest algae. Macroalgae and copepods have a sort of symbiotic relationship. The macroalgae provides a home for the copepods, and the copepods keep the macroalgae clean. Possibly the most common reason hobbyists find out about copepods is to feed finicky fish. Fish such as Mandarin Dragonets and Leapord Wrasses rely on copepods as a food source. Without copepods, these finicky fish often starve to death. While there are captive-bred mandarins that eat frozen food, it is still important to have copepods that they can munch on between feedings. Copepods also find their way into corals and feed them too. Another great benefit of copepods is that they eat pest algae. They can help keep your aquarium clean of film algae and other nuisance alga. The reason copepods are kept in a refugium is so that even if the population in the main display is depleted, there are still copepods to make their way into the display and replenish the population. This is especially important if you are keeping a mandarin. Although mandarin can eat a lot of copepods in one day, it won't be able to eat the copepods in the refugium, ensuring there will always be copepods in the system.
Overall, refugiums help keep aquariums stable mostly with copepods and macroalgae. Copepods and macroalgae serve so many benefits, as you read above. Having a separate part of your aquarium just for these two organisms accomplishes a lot from nutrient control to feeding your fish. Refugiums can also be a habitat for amphipods and beneficial bacteria. All these things are great, but do you need a refugium for your aquarium?
Will a refugium benefit your aquarium?
Hopefully, you understand the purpose of a refugium. The next question is whether a refugium will benefit your specific aquarium. As established, there is nothing that has to be done in order to run an aquarium. It all depends on what you want out of your aquarium. If you have problems with high nutrients, a refugium will certainly benefit you. That's one of the largest benefits of having a refugium. If you plan on keeping a mandarin or other similar finicky fish, a refugium will help keep your fish healthy by maintaining a stable copepod population. It is almost a must to have one if you have or want to have a mandarin dragonet. Without a refugium, the mandarin could completely deplete your copepod population, leaving the fish to slowly wither away. Another way a refugium can benefit an aquarium is by making it more autonomous.
If you cannot put as much time into your aquarium as it requires, especially with water changes and removing algae, a refugium can help big time. Algae is quite possibly the most common issue in the saltwater aquarium hobby. It can ravage tanks and make them look ugly. Algae can also be a difficult problem to fix, but a refugium can help by growing macroalgae to combat the pest algae. We already went over the purpose of refugium, so if any of the purposes of a refugium can apply to your aquarium, a refugium will benefit you.
There are few aquariums that wouldn't benefit from a refugium, but there are some. If none of these things apply to your aquarium, a refugium may not be worth it for you. There are still other benefits to having a refugium such as overall stability, but it could be futile unless you have one of the mentioned issues or needs. However, at least one of the things mentioned prior applies to most reef aquariums and aquarium keepers. Chances are that a refugium would significantly benefit you.
Do you absolutely need a refugium? No, not at all. Would a refugium benefit your aquarium? There's a high chance it would. If you want to start a refugium, AlgaeBarn has you covered. Checkout this awesome refugium starter pack
and make yourself an incredible refugium!