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3. Saltwater Aquarium Refugium - Required? A Helpful Guide. The Good, The Bad, The Ugly

Saltwater Aquarium Refugium - Required? A Helpful Guide. The Good, The Bad, The Ugly

• Feb 14, 2019
• PalaciosAn
•   2635        1      0

What is a refugium for saltwater tanks?

Sometimes referred to as a "fuge" refugiums are a safe area dedicated to growing species without the fear of them being picked on or eaten by others to the point of extinction. So why would something like this be needed for a saltwater aquarium? I keep all of the species in my tank safe, but do you?

Pods also know as Copepods or Amphipods grow in your tank, it's practically unavoidable, you may not know they are present, but they are in your display tank. Pods usually come out at night to prevent being eaten by your fish or invertebrates. They are considered a scavenger cleanup crew, while most people think that they are only eating detritus or leftover waste in your tank that is true, but they will practically eat whatever they can get ahold. They also serve as an excellent live food source for your aquarium.

The pods in your display tank will be hunted upon. If you have Seahorses, Dragonets, some types of Gobies like Mandarin Gobies or Wrasse, which are considered active hunters, then they are continually being hunted upon. Many fish species will benefit from a healthy pod population, and just about all carnivorous and omnivorous species will enjoy a taste pod. Your pod population in your display tank could become endangered or, in cases through very rarely, could even become extinct. Some fish like Draginets and Mandarin Goby needs a healthy population for them to survive.

These pods are a natural food source that many fish and corals have come to rely on having available. Ideally, it would be great if you could provide this food source to your tank without having to worry about them being eradicated from your tank. That is where a refugium comes into play. It provides a safe area for pods to grow. Refugiums can be plumbed into your aquarium, allowing the pods to escape the refugium and wonder into your display tank, which at that point, they become fair game for all fish and corals.

What is the purpose of a refugium?

The primary purpose of a refugium is to provide a safe haven for species to grow and reproduce without worrying about being eaten or picked on. In the saltwater aquarium hobby, most people are interested in increasing Copepods, Amphipods, or plants/microalgae to help feed their aquarium or help control nutrients with plants.

What are the Benefits of a Refugium?

I mentioned that it is rare for pods to become utterly extinct from your aquarium, what are the benefits of having a refugium?

By creating this safe area for your pods to thrive and reproduce, enables your tank to get a steady source of pods, ideally, you would want a large number of pods in your tank to create a stable, healthy and natural food source for your fish and corals. Other benefits are planted refugiums, where plants can also grow and thrive in an environment where fish are not picking at them.

Plants in a refugium can help absorb nitrates and phosphates in your tank as well as contribute to your pH level in your tank. They can also be used as a natural filtration for the aquarium. We will go into more detail on each of these topics below.

Do You Have to Have a Refugium to be Successful?

No, you do not have to have an aquarium to have a successful saltwater aquarium. Just using a quick poll online, over 77% of aquarium have some sort of refugium in their aquarium setup. So less than 23% of people in the hobby* do not have a refugium. I have also personally seen many setups that did not have a refugium, and they were awesome setups.

I think the benefits outway not having a refugium. With that said, they do require space, and you may not have space for one, then you just don't have space, and there is nothing you can do.

* Data is based on the people who interacted with our online poll.

Requirements for Growing Copepods in a Refugium?

Pods, also know as Copepods or Amphipods, do not have too many requirements to grow properly within your aquarium. They need a safe area where they will not be eaten by other species to allow them to breed safely. If you do not have plants in your refugium, it is also wise to have Pods Hotels. The hotels which can easily be made using corrugated plastic by cutting them into small maybe 2" by 2" squares and stacking 5-10 of them onto one another and they weighing them down to stay in a spot in your refugium. This gives the pod a home that they can crawl into and make into a hope. If they feel safe and have a food source, they will breed.

You do not have to have pods Hotels for them to breed, you can also have rock rubble within your refugium to allow them to make homes in as well.

Some people will also have plants that allow the pods to feel safe as well. Plants have their requirements, which we will go over next.

Pods do not need any light source to survive. They tend to be more active in areas they feel safe in and, in most cases, are more active in the dark. You can easily create a pod with no lights that will create an ideal breeding ground for pods to grow raiser their families and start the cycle all over. Some will venture out into the deep blue (aka display tank to be eaten).

Pods do require food. They are opportunistic feeders. They eat most things that drift their way, unlike most species, they prefer the food to come to them versus going out and searching for food. Just like any other food, the nutritional value of pods is based on the quality of food that they eat. If you do not feed your pods and they primarily eat detritus and waist, then their nutritional value will be less then if they are feed phytoplankton. If pods survive the trip to your display tank, they will have access to the leftover food that is not eaten by the species in your tank.

Pods can survive on detritus and waste that lingers into the refugium, but they will thrive and breed more quickly with a quality food source available like live phytoplankton.

If you want, you can play some music to get them in the mode, but that is optional.

Requirements for Growing Plants in a Refugium?

Having plants in a refugium can help scrubbers the water to help control your nutrient level within your aquarium like nitrate and phosphate levels. While the plant are absorbing these nutrients in the water, for them to be considered a true nutrient export, you must prune or harvest the plant to remove the nutrients from your tank. At any point, if the plant dies, the nutrients will be released back into your aquarium.

By these plants or microalgae consuming the nutrients in the water by doing so, it also prevents unwanted algae that also flourish by absorbing these nutrients in the tank from growing or will at least slow them down how they have to compete with the refugium.

Unlike a Copepods or Amphipods hatchery, which does not require lighting, a planted refugium does require lights. The beautiful thing is that the lighting requirements are not huge for a planted refugium; it can be as simple as a bulb and a light fixture. While it is true, just about any bulb will provide plant growth, not all bulbs are created equal. There are specific lights that were designed for refugium plant growth. These lights have shown elevated levels of growth versus your typical bulb and light fixture.

Faster growth also means more rapid nutrient absorption as well. So depending on your needs and budget, there is a wide range of options from the typical $30 Setup of a bulb and fixture to the top of the line Kessil Refugium Grow Light, which will run over $200. There are also lots of other options that you can look at, which were designed for aquaponics or hydroponics use as well. I use a small LED grow lights that were intended for aquaponics, I paid about $25 for it, but you can see the current price here.

Plants are also a good home for Copepods or Amphipods. They will feel safe living within the plants.

Some of the most common plants used in refugiums are Chaeto, Mangroves, Caulerpa, Dragon Tonge, Sea Lettuce, and Seagrass. There are many other types of plants and microalgae to choose from, and each different species absorbs nitrates and phosphate at different rates. Each species will also have its requirements, individual benefits, and some have features that may be considered harmful. So do your research when choosing a plant for your refugium. It seems like the most common plant used in a refugium seems to be Chaeto.

Some macroalgae like Caulerpa can go asexual and spread outside of your refugium by releasing spoors and can become problematic due to spreading quickly. Some consume calcium and compete with your corals.

Need to buy some plants for your refugium? Check out Alage Barn they are an excellent source for microalgae, and they also provide clean Chaeto, so you do not have to worry about any hitchhikers being introduced to your tank from your microalgae.

Lighting Cycle for Refugiums

Plants and microalgae do not grow well in a 24-hour light cycle. Eventually, most of the plants will die off if you leave the lights on 24-hours a day. Photosynthesis requires at least six-hour period of darkness for proper respiration and growth.

When the lights are off, plants will produce carbon dioxide, which causes pH to decrease.

The pH levels in an aquarium fluctuate throughout the day, usually early in the day before the lights coming on will be your lowest pH level and right before your lights turn off will be the highest level. When your lights turn off, your pH will start to drop. By running a reverse cycle on your refugium, it helps stabilize your pH a little more. Does this mean my pH will be stable? No, it means the low to high swing will be shorter.

So what does it mean to run a reverse light cycle? What it means is that when your aquarium lights turn off, your refugium lights should turn on. When your aquarium lights turn off, your refugium lights should turn off. It's that simple.

Type of Substrate for a Refugium

There are four basic options for a substrate for your refugium. Ok, so there could be more, but these are the more common options, so let's discuss them.

Bare Bottom Refugium

This is a standard option for a lot of people, using a bare bottom refugium make it easy to clean your refugium of any unwanted debris.

The significant advantage of bare bottom refugiums is easy of maintenance.

Refugium Deep Sandbed (DSB) Substrate

With deep sandbeds, you have additional filtration and surface area for bacteria to grow on. The top inch of the sandbed will be actively growing bacteria. When I say deep sand bed, I am talking about 5 inches thick sandbed. These are the type of sandbed that you do not want to disturb to allow the proper bacteria to grow.

Some plants need some a substrate to grow in, and sandbeds are a common choice. Sandbeds can also help some invertebrates like worms that like to burrow into the sand.

Negatives things about a DSB are that it can trap nutrients and when disturbed and leaks large quantities of nutrients into the water causing large swings in the water parameters. The significant fluctuation in parameters can cause issues with some species.

Refugium Miracle Mud Substrate

People either love this stuff or hate it. There are not too many in-between people. I have personally never used it but have seen some fantastic tanks who use Miracle Mud.

Miracle Mud continuously replenishes the natural mineral and trace elements into the aquarium water, which is consumed by corals, creating the ideal environment for fish, corals, and other invertebrates.

The biggest complain that I hear from people is when they have to replace the Miracle Mud is a colossal pain in the rear. Miracle Mud is something that has to be partially replaced every so often, and most people give up on Miracle Mud when it comes to time to replace part of it.

Here is a tip, get three containers that fit into the refugium or build three custom containers out of acrylic that fit your refugium area. Fill each of the containers with Miracle Mud, and when it comes to time to replace part of the Miracle Mud, take out the containers closest to you out of the refugium, slide the other two containers closer to you. Clean out the container that you took out of the refugium and add new mud in the container, then place the container with the new mud in the slot furthest from you. You know that the oldest must is closet to you, and the newest mud is further. It keeps your refugium clean, and being able to take out the container from the refugium makes it easier to deal with the mud.

The issue most people encounter is scraping the mud out of their sump. You have to be hunched over for an extended period, and it's just a pain. A little effort beforehand can make the process much easier in the future.

Refugium Live Rock Substrate

Live rock in your refugium allows you to increase the biological filtration in your tank—the more surface area where good bacteria can grow on, the better. Rubble rock for the substrate is a great option that not only creates surface area and creates homes for Copepods or Amphipods. There are no real cons to a rubble rock. I would try to avoid large rocks to give more room for plants.

Different Types of Refugiums

Refugiums come in different types and styles. The most common refugiums are located in the sump. You can also have them as standalone refugiums that are tied into your system.

I like the standalone refugiums, and if possible, I like them to be located above the display tank to allow them to be gravity fed into the display tank, or you can also create a surge flow into the display tank.

I am not as a big fan of the hangover the back (HoB) refugiums because sometimes they can be challenging to work on, and the lights can bleed into the display tank. The nice thing is that they gravity feed into the display tank.

Why do I think gravity feed refugiums are better than refugiums that need a return pump to get the water back into the display tank. The issue with a return pump taking the pods back to your display tank is that the live pod has to go through the pump. I see people who claim that 20-40% of the pods that go through the pump died. I am not sure where the numbers are coming from I would think that at least 50% of them would die if not more and then another 20-40% would be injured in the process. I am pulling all my numbers out of my @ss they are just assumptions.

Even if it right that 20-40% of them die, if they are coming in through a gravity feed overflow, then they all survive the trip to the display tank. Many of them die instantly when they get there due to unfortunate timing and hungry fish, but that is a different issue.

There are also display refugiums where you turn a tanks display into a natural refugium. Similar to a freshwater planted tank, it will require pruning.

Another option for people who do not have space for a refugium is to simply add some egg crate to the back 2 or 3" of the tank to prevent fish from going back there, add some rubble and a few plants, and you have an instant refugium in your display. Don't want to see the egg crate create, build egg crate cubes with rubble inside the cubes, and then cover the cubes with larger rocks so that you do not see the egg crate. If you have a large enough tank, you may be able to create multiple cubes through the tank. You will not be able to create grow any plants in the cubes, but you will create small safe areas for pods in your tank.