What Is A Refugium

What Is A Refugium?

If you are a new aquarium owner, you must be wondering “what is a refugium?” A refugium is a separate compartment either within the saltwater or reef aquarium or completely outside of the tank that is used to continuously cycle and filter the water from your aquarium. The subsystem usually hangs on the side or stays hidden beneath the aquarium in a cabinet.

The refugium recreates a natural environment which usually includes live rock, a mud or sand bed and macro-algae. Through this process, water is filtered naturally without having to cycle a tank as frequently. This allows for better algae control and dramatically lower nitrate and phosphate levels.

Why Use A Refugium?

A refugium is mainly used as a means through which we can filter water, process nutrients and export waste from the main tank. The biological filtration method reduces nitrates and phosphates found in water. The process creates an environment that is good for the growth of your aquarium fish and delicate reef and also minimizes the need to change the water in the aquarium.

A refugium can also be used to grow feeder organisms such as copepods, amphipods and small feeder fish which can also be used to provide food for your aquarium fish. These feeder organisms are allowed to grow and reproduce in this protected environment and gradually introduced to the main tank.

Being separated from the main tank, these environments can also be used for protection purposes when introducing new or delicate inhabitants to the tank. The compartment allows the new inhabitants time to adjust to the environment before being released into the main tank.

How Does A Refugium Work?

As we mentioned before, a refugium is mainly used to filter water. Most of the uneaten fish food, fish waste, and other dead organisms settle in the sand beds. The crustaceans that reside in the sand beds such as copepods and amphipods then feed on the foods accumulating at the bottom. By eating the food, the organisms help in maintaining water quality.

As the crustaceans feed on the matter, they grow and reproduce. As they increase in number, they provide an excellent source of natural food for the fish in the aquarium. Adding macro-algae such as Cheatomorpha and Caulerpa can also be beneficial in a refugium. They will absorb Nitrates and Phosphates from the aquarium water and also help prevent the spread of nuisance algae into the main aquarium. Mangroves are also another additional option for reducing nutrients but can have additional care requirements.

Adding a light source to the refugium at night can also help avoid large pH drops in your main tank. The light provided for the algae enables them to resume the process of photosynthesis while your main tank is in the dark.

What Is The Best Refugium Setup?

There are several different types of refugiums available on the market. Your tank layout and the space availability will usually determine which type is best for your aquarium. Most models provide “do it yourself options,” and others come already incorporated in the main tank or sump pump.

In Tank Refugium

In tank refugiums come with inbuilt compartments that we can use to create a separate environment. It has adjustable sliding brackets to allow closing and opening. It is thus easy to set up and maintain. The system facilitates a gentle flow of water inside the fish tank and keeps all the content of the subsystem away from the return pump and other chambers. The main disadvantage is that it can be very expensive.

Sump-based Refugium

Sump-based Refugium designs entail having a separate stand-alone system which is usually contained in a cabinet under your main tank but still connected to the main aquarium. The refugium is one of several compartments in the sump which used in combination with other equipment helps in the filtration process.

Compared to the HOB refugium sump systems can be hidden away in a cabinet or adjoining room. However, the space required and the cost for the additional equipment can be a deterrent for beginners and hobbyists.

Hang on Back Design (HOB)

The Hang on Back refugium model has the system compartment at the back of the aquarium. The subsystem connects to the main water tank by using holes in the tank or a u-tube. HOB refugiums are easier to manage as they are more accessible and affordable.

However, if the system is not set up correctly, there may be occasions where the water flow is unstable which can cause your tank nutrients to become unbalanced. The hang on back refugium can also take away from the overall appearance of your tank as it is not easy to hide.

What To Put In A Refugium?

Refugiums can be set up many different ways but include live rock, mud or sand substrate, and macro-algae. Below we have included some of the best elements to include in your subsystem:

Best Macro-algae For Refugiums

Macroalgae are significant in the subsystem as they help in consuming all the nutrients. The practice helps in keeping the water clean. The best macro-algae are:

Best Refugium Substrate

For refugium substrates, sand is perfectly acceptable but refugium mud is the best choice due to its size and texture allowing microorganisms to burrow and reproduce and its ability to restore trace elements. Use 1 to 2 inches of depth to create nitrate-reducing anaerobic zones within the substrate. Some of the refugium mud choices we recommend are:

Best Plants for Refugiums

  • Mangrove
  • Spiny seaweed
  • Gracilaria
  • Green finger plant

What Size Refugium Do I Need?

Size is an essential factor to put into consideration in decision making. Some people prefer the recommended 10-50% of the display water volume. However, the bigger the refugium, the easier it is to maintain.

Refugiums that are too small and don’t allow enough volume of water to flow through won’t have the needed effect of reducing Nitrates and Phosphates. Basically it just depends on how much room you have available.

How Much Flow Through The Refugium?

A slow rate of water flow is recommended for any refugium. It gives enough time for the water to come into contact with the macro-algae which we have included to absorb the unwanted nutrients.

When there is a lack of a good flow of water, the macro-algae will not be able to reduce the nitrate and phosphate levels which could lead to the death of the fish in the aquarium.

In conclusion, a refugium can be an essential part of your aquarium set up by reducing water changes and increasing the overall health of your aquarium. The space required and extra equipment expense can be a detriment to some tank owners.

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