refugium by Sean McGrath

Why you should add a refugium to your aquarium

Why you should add a refugium to your aquarium…if you can

A refugium is a great thing to add to your aquarium set-up…if you can. Think of the refugium as a nature preserve within the confines of your aquarium system. It’s a small area set

refugium by Sean McGrath

Image by Sean McGrath

aside for macroalgae and tiny invertebrates to flourish.

Adding a refugium to your aquarium can provide the following benefits:

  1. Nitrate removal–macroalgae in the refugium will treat excess nitrates in the water like plant fertilizer–the more algae you grow, the more nitrate you will export from your aquarium system. A fully functioning refugium will purify your aquarium water in this way

  2. Boost the population of beneficial invertebrates in your aquarium— Tiny little invertebrates (copepods and amphipods) can be found in most mature saltwater aquariums.  The problem (if you’re a copepod or amphipod) is that they’re a natural and highly nutritious food source for your fish–and the fish in your tank will eat any ‘pods they can catch. A refugium provides an oasis for these tasty morsels to grow without being munched on. Over time, a certain number of these ‘pods make their way into the display area of your aquarium and boost the biological activity of your aquarium (or become part of the food chain). Either way, that’s a good thing.

  3. pH balance–Isn’t there a deodorant with the tagline pH balanced…for women? Sorry, that was a tangent–A refugium won’t help you smell better, but it can help with the pH balance of your tank–here’s how. Many people set their refugium light to operate when the rest of the tank is dark. When the lights are on, plants and algae (including symbiotic zooxanthellae in your corals and clams) turn light and carbon dioxide into sugar, releasing oxygen. This chemical reaction can actually change the pH in your tank. Without a refugium set up on the opposite schedule, the pH of your tank will vary between day and night. Setting up your refugium to be on when your tank is off can help balance those pH swings, making your tank more stable than it would be otherwise.

Location, Location, Location

Now that I’ve touted some of the benefits–where are you going to put your refugium? There are two common places to connect a refugium to your aquarium system:

1) Most aquarists with a sump prefer to dedicate an area within their sump as the refugium area. That way it is connected directly into the aquarium’s existing plumbing and actually looks and acts like a part of the filtration system.

2) Another popular and easy way to add a refugium to almost any tank is to use a Hang-on-the-back style refugium (hang-on-the-back is sometimes abbreviated HOB). You can get these from your local fish store or favorite online supplier.


To sum it up, you should add a refugium to your aquarium system if you have the space and money. They are a great way to improve the quality of the water in your aquarium system naturally. This article was just intended to be a introduction to refugiums. For more in depth information, here is a helpful Youtube video.


As a disclaimer, the video is long but it is helpful:

Please note, the images in this post (not the video) are from Amazon and contain affiliate links–which means if you click on them–they take you to Amazon’s site–and if you buy something a small amount of money is generated for me. I recommend, however, for a complex purchase like this that you buy from your preferred aquarium store so you can benefit from the helpful advice and information they can provide.

Photo credit: Sean McGrath

Written by Albert B. Ulrich III.

Leave a Comment