What Does A Refugium Do?

Refugia continue to become more and more popular in the
marine aquarium hobby. This is in large part because of a growing reliance on
natural water filtration/treatment methodologies. But, mainly, this is because
they actually work.

The typical refugium has multiple functions. However, their
most basic purpose is to provide refuge for organisms that would be quickly
consumed if kept in the so-called main tank. This could be plants, animals or
both. Traditionally, refugia are used mainly to protect and nurture macroalgae
and microcrustaceans. These two are mutually beneficial, as a healthy, thick
bed of seaweed provides an enormous amount of prime habitat for the “pods”
(especially copepods) while the pods keep the “macro” clean of detritus and
microalgal films.

The benefits to the system are wholistic. As they grow,
macroalgae remove unwanted, excess dissolved nutrients (e.g. nitrate and
phosphate) from the water. Particularly when run on a reverse light cycle (day
and night cycles that alternate with the main tank), the removal of CO2 during photosynthesis serves to stabile pH throughout the whole system.

The pods help to maintain a hygienic environment by
consuming detritus. This can work quite well in a heavily planted refugium
because suspended organic matter settles out or gets trapped within the dense
macroalgal bed.

Finally, macroalgae (especially highly palatable
varieties such as sea lettuce and ogo) are fed out to herbivores in the main
tank as the crop in the “fuge” reaches it carrying capacity. Excess pods, both
adult and juvenile, continuously spill out from the fuge into the main tank
where they may be consumed by various hungry inhabitants. In this respect, what
refugia really do is convert bad stuff like excess nutrients, microalgae
and detritus into highly nutritious, natural live foods for your fish and