Creating a refugium in a saltwater aquarium can be a fantastic way to add extra filtration, more beneficial bacteria, and a space for microorganisms to flourish in your saltwater aquarium. You can create a refugium in many different ways, and this guide will cover some of the most common ways to do so. With aquarium keeping, there is no single solution that works best, especially when discussing such a broad topic as how to set up a refugium. There are a million and a half opinions, that come from a good place, but it can be challenging for new hobbyists to find solid ground in an ocean of different experiences. This article is designed to make setting up a refugium a little less stressful.
What is a Saltwater Refugium?
We are always battling nutrient levels in aquariums thanks to our feeding regime. A refugium is a section in your aquarium system that is dedicated to growing macroalgae and a haven for microorganisms such as copepods. Macroalgae uptakes nutrients such as nitrates and phosphates which come from food and animal waste. Just like how plants in a freshwater aquarium use nutrients to grow, the macroalgae do the same except in a marine environment. The macroalgae “holds” the nutrients and we remove them by trimming the macroalgae and physically removing it from the aquarium. Just like freshwater plants, macroalgae will require light to grow, which we will discuss later in this article.
Copepods are very small invertebrates that are often food for fish and other animals in our display tanks. A refugium is a place in your aquarium that is safe from predation because fish don’t have access to it. Copepods and other small invertebrates use this space as a refuge and this allows their populations to multiply and grow without fear of getting eaten. Eventually, these populations of microorganisms will make their way back into the display aquarium, where they become food for fish such as gobies, blennies, wrasses, and many others.
Other Refugium Benefits
Besides nutrient intake, a refugium that has a light interval opposite to the aquarium’s display section will keep your pH levels more stable. pH rises throughout the day due to plants and algae photosynthesizing and creating more oxygen. Photosynthesis does not happen at night, and you will likely see a drop in pH during this time. If you run a refugium on a lighting interval opposite to your display aquarium, there will always be a light period, which means there will always be photosynthesis occurring, and increased levels of oxygen, which will raise your pH level.
Many aquarists use this method in an attempt to keep their pH levels from swinging. However, pH levels swing naturally through the day and night cycle so it’s not a mandatory thing to do. You are more than welcome to run your refugium on the same lighting cycle as your display tank.
Do I Need a Refugium?
No, you do not need a refugium to successfully run a saltwater fish tank or a reef tank. However, the benefits of keeping a refugium make it a very attractive addition to your fish tank. I still recommend conducting water changes to remove excess nutrients, detritus, and to supplement your aquarium with fresh minerals. A refugium is an additional tool we can use to help keep our water parameters in line and as an additional source of food for your fish. It is not a complete package solution to get out of conducting water changes.
How to Make a Refugium for Saltwater Aquarium
Before we dive into the specifics of setting up a refugium, I want to emphasize that it’s best to hold off on adding lights and macroalgae into the refugium before the aquarium is established with fish and coral. Likely, the macroalgae will not be able to sustain itself if the aquarium is too “new” and there are not enough nutrients for it to consume. I recommend setting up and having all the components of the refugium ready to go and adding your macroalgae once there are signs of increased levels of nitrates and phosphates.
You can make a refugium as complex or as simple as you want. I prefer keeping things as simple as possible.
Refugium in Sump System
If you have a sump system, you may want to use or convert your second chamber into a refugium. If you are just starting a fish tank, it’ll be easy to insert everything you need to get started. However, if you are thinking of converting the second chamber, you will likely need to turn off your return pump before adding sand and keeping it off to give the sand time to settle. The supplies needed for a sump refugium aren’t very complex. The following are what I choose when setting up a refugium in a sump:
- Macroalgae (Chaetomorpha)
- Live Rock – Nature’s Ocean Coral Base Rock
- Refugium Light (Kolem COB LED Grow Light, Kessil H80 Tuna Flora LED, Relassy Waterproof Plant Light)
- Live Sand – CaribSea Fiji Pink (optional)
- Circulation Pump – Hygger Mini Wave Maker (optional)
Live Sand for Refugium (optional)
There is a lot of back and forth on what is important in a refugium. From the amount of reading that I have done on the topic, I have learned that the safest route to avoid creating a detritus trap or other problems later on is to set up your refugium with live rock, macroalgae, and lighting, but without adding any live sand. Detritus will likely settle somewhere in your sump, and it’ll be much easier to clean out if there isn’t any sand present. If you would like to have sand in your refugium, I would recommend having no less than 3″ to provide more space for bacteria to colonize and break down detritus. I have used CaribSea Fiji Pink Sand in my refugium, and it hasn’t caused any problems for me.
Live Rock
I recommend adding appropriately sized pieces of live rock into your refugium. The live rock will provide more space for beneficial bacteria and will be a home for all the tiny invertebrates and other critters. I would avoid pieces that are too large because they will inhibit the growth of your macroalgae. I would also avoid adding rock rubble because detritus will enjoy settling around the rock rubble.
Lighting
I provided three different lighting options that should work for your refugium. The first is the Kolem COB LED Grow Light. This should do incredibly well in aiding the growth of green macroalgae such as chaetomorpha. Chaeto absorbs the red coloration, which is what this light provides. The Kessil H80 Tuna Flora Light does something very similar, except is a more well-known brand in the aquarium trade. Lastly, I added the Relassy Waterproof Plant Light which provides a more well-rounded spectrum of lighting. If you’re looking to grow red-colored macroalgae such as the PomPom Macroalgae, you will do better with cool colored lights.
Circulation Pump
Chaetomorpha and a few other macro species benefit from tumbling in a refugium. A circulation pump may or may not be needed depending on the size and shape of your sump system’s second chamber and the amount of flow going through it. If you see that the bottom portion of your chaeto is dying out or you’re getting a buildup of gunk within the chaeto, you may want to encourage it to tumble, which a circulation pump can assist with.
Refugium For Hang On Back Filter
If you’re working with a smaller reef tank or saltwater aquarium, you’re likely not working with a sump system. As of this writing, I am running a small reef tank with a hang-on back refugium. For this to be successful, I am running an AquaClear 70 Hang-on Back Power Filter as my main source of water flow and filtration. I have the main compartment of the power filter filled with smaller pieces of live rock and chaetomorpha growing above it. A small 5W UPETTOOLS Aquarium Light provides the light needed for the chaeto.
I chose the AquaClear Power Filter for this, mainly because of the size of the main chamber. I like being able to gut just about everything from the filter and customize it to my needs. Other Power Filters can work, but I have always had a soft spot for this brand. You can check out other AquaClear Power Filters, their specs, sizes, and GPH ratings by clicking the link provided.
In Tank Refugium
You can setup a refugium inside of your display tank. It might end up being the most interesting part of your display. The first thing you will need for something like this is a container. The CPR Aquatic in Tank Refugium may be just what you are looking for, but I have also heard people using something as simple as a plastic breeder box to set this up. Be mindful that the suction cups on the CPR Aquatic in Tank Refugium are not incredibly strong.
Once you have your container, you’ll probably be limited to only using small live rock pieces and macroalgae for this type of refugium. Some might even call this a glorified algae reactor instead of a refugium. For the sake of this article, let’s say it’s a fuge because it will still be a haven for microorganisms. You may get away with adding sand into this, but I would be worried about too much weight and sand sneaking out through the grates.
Lastly we need to think about lighting. It’s possible that this type of refugium will get all the lighting it needs from the display light. I would probably avoid adding an external light because that will likely bleed into the aquarium. If too much light bleeds into your aquarium, you’ll likely see algal blooms forming in your display.
Final Notes
There are plenty of options when it comes to setting up a refugium. You can get one set up in a sump, hang on the back filter, or even in your display tank. The options are there. Do you need a refugium for a reef tank? No, of course not but they are incredibly fun to work with and it’s very rewarding to say you grew live plants in a saltwater environment. One thing we have not covered is cryptic refugiums. These are unique because they use zero lighting, and instead use different sponges and other filter feeders to aid in cleaning your water.
Image by Coughdrop12 on wikiMedia
