fishkeeping Fishkeeping is a popular hobby, practiced by aquarists, concerned with keeping fish in a home aquarium or garden pond. There is also a piscicultural fishkeeping industry, serving as a branch of agriculture. Origins of fishkeeping Fish have ...

, a refugium is an appendage to a marine, brackish, or freshwater fish tank that shares the same water supply. It is a separate

sump A sump is a low space that collects often undesirable liquids such as water or chemicals. A sump can also be an infiltration basin used to manage surface runoff water and recharge underground aquifers. Sump can also refer to an area in a cave ...

, connected to the main show tank. It is a " refugium" in the sense that it permits organisms to be maintained that would not survive in the main system, whether food animals, anaerobic denitrifying bacteria, or photosynthesizers. For some applications water flow is limited in order to protect plants or animals that require slow flow. The refugium light cycle can be operated opposite to the main tank, in order to keep total system pH more stable (due to the uptake of acid-forming CO₂ by

photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...

occurring in the refugium during its "daylight" hours). One volume guideline for a refugium is 1:10 main tank volume. A refugium may be used for one or more purposes such as

denitrification Denitrification is a microbially facilitated process where nitrate (NO3−) is reduced and ultimately produces molecular nitrogen (N2) through a series of intermediate gaseous nitrogen oxide products. Facultative anaerobic bacteria perform denitr ...

, nutrient export,

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

production, circulation, surface agitation to improve oxygen exchange with the atmosphere or even aesthetic purposes.

Construction

Tropical marine refugiums often contain live rock and live sand, macroalgae, and sometimes scavenger microfauna such as micro brittle stars, tiny sea stars such as ''Asterina'', snails, and worms.Calfo, A: "Book of Coral Propagation". Reading Trees Publication, 2009. To achieve maximum biological filtration through uptake of nutrients by macroalgae/mangroves, strong lighting is often utilized in the refugium. In this fashion, macroalgae algae growth is encouraged, competing with nuisance algae which would otherwise thrive in the main/display tank. Some also use refugiums to raise tiny

brine shrimp ''Artemia'' is a genus of aquatic crustaceans also known as brine shrimp. It is the only genus in the family Artemiidae. The first historical record of the existence of ''Artemia'' dates back to the first half of the 10th century AD from Urmia La ...

mysis shrimp Mysida is an order of small, shrimp-like crustaceans in the malacostracan superorder Peracarida. Their common name opossum shrimps stems from the presence of a brood pouch or "marsupium" in females. The fact that the larvae are reared in ...

ostracod Ostracods, or ostracodes, are a class of the Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 70,000 species (only 13,000 of which are extant) have been identified, grouped into several orders. They are small crustaceans, typic ...

amphipod Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods range in size from and are mostly detritivores or scavengers. There are more than 9,900 amphipod species so far descr ...

copepod Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...

s and

isopod Isopoda is an order of crustaceans that includes woodlice and their relatives. Isopods live in the sea, in fresh water, or on land. All have rigid, segmented exoskeletons, two pairs of antennae, seven pairs of jointed limbs on the thorax, an ...

s for delicate fish like

seahorse A seahorse (also written ''sea-horse'' and ''sea horse'') is any of 46 species of small marine fish in the genus ''Hippocampus''. "Hippocampus" comes from the Ancient Greek (), itself from () meaning "horse" and () meaning "sea monster" or " ...

s and

dragonet Dragonets are small, percomorph, marine fish of the diverse family Callionymidae (from the Greek ''kallis'', "beautiful" and ', "name") found mainly in the tropical waters of the western Indo-Pacific. They are benthic organisms, spending mos ...

s to feed on. A sump is an additional tank often kept under the display tank that serves to house filtration and other miscellaneous equipment such as protein skimmers, reaction chambers, hoses, heaters and the like. This is especially common for show tanks and reef tanks. In addition to housing critical equipment, the sump serves to add volume to the total system; mitigating the effects of nutrient buildup or unintentional introduction of foreign substances. Tropical freshwater refugiums often contain large amounts of aquarium plants, primarily ''

Vallisneria ''Vallisneria'' (named in honor of Antonio Vallisneri) is a genus of freshwater aquatic plant, commonly called eelgrass, tape grass or vallis. The genus is widely distributed in tropical and subtropical regions of Asia, Africa, Europe, and Nor ...

'', ''

Anubias ''Anubias'' is a genus of aquatic and semi-aquatic flowering plants in the family Araceae, native to tropical central and western Africa. They primarily grow in rivers and streams, but can also be found in marshes. They are characterized by broad ...

'', '' Cabomba'', ''

Echinodorus ''Echinodorus'', commonly known as burhead or Amazon sword, is a genus of plants in the family Alismataceae, native to the Western Hemisphere from the central United States to Argentina. Its scientific name is derived from Ancient Greek ' – " ...

'', ''

Microsorum ''Microsorum'' is a genus of ferns in the family Polypodiaceae, subfamily Microsoroideae, according to the Pteridophyte Phylogeny Group classification of 2016 (PPG I). The species are tropical. Like most ferns, they grow from rhizomes, ...

'', ''

Cladophora ''Cladophora'' is a genus of reticulated filamentous Ulvophyceae (green algae). The genus ''Cladophora'' contains many species that are very hard to tell apart and classify, mainly because of the great variation in their appearances, which is a ...

'',

Java moss Java moss is a common name for several plants and may refer to: *''Taxiphyllum barbieri'' *''Vesicularia dubyana ''Vesicularia dubyana'', known as Java moss or Singapore moss, is a species of moss native to Asia. It is common in the aquarium tra ...

and ''

Fontinalis ''Fontinalis'' is a genus of submerged aquatic mosses belonging to the subclass Bryidae Bryidae is an important subclass of Bryopsida. It is common throughout the whole world. Members have a double peristome with alternating tooth segments. ...

'', but like marine tanks they often contain scavengers such as several species of prolific snails which are often Malaysian trumpet snails, Ramshorn snails and ''

Physa ''Physa'' is a genus of small, left-handed or sinistral, air-breathing freshwater snails, aquatic pulmonate gastropod mollusks in the subfamily Physinae of the family Physidae.MolluscaBase eds. (2021). MolluscaBase. Physa Draparnaud, 1801. Ac ...

'' and prolific shrimp such as

cherry shrimp ''Neocaridina davidi'' is a freshwater shrimp originating from eastern China and northern Taiwan and introduced in the rest of Taiwan, Japan, and Hawaii, which is commonly kept in aquaria. The natural coloration of the shrimp is green-brow ...

. Some use refugiums to raise microfauna ''

Daphnia ''Daphnia'' is a genus of small planktonic crustaceans, in length. ''Daphnia'' are members of the order Anomopoda, and are one of the several small aquatic crustaceans commonly called water fleas because their saltatory swimming style resembl ...

'', ''

Moina ''Moina'' is a genus of crustaceans within the family Moinidae. The genus was first described by W. Baird in 1850. They are referred to as water fleas, but are related to the much larger ''Daphnia magna'' and the larger ''Daphnia pulex''. This ...

'' and ''

Gammarus ''Gammarus'' is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimal conditions, particularly i ...

'' to supplement the diets of the fish in the main tank, particularly fish that are picky about their diet, such as freshwater

pipefish Pipefishes or pipe-fishes (Syngnathinae) are a subfamily of small fishes, which, together with the seahorses and seadragons (''Phycodurus'' and ''Phyllopteryx''), form the family Syngnathidae. Description Pipefish look like straight-bodied seah ...

. In home aquariums, the refugium is typically located in the cabinet underneath the main tank. By confining the plants and creatures to the refugium, the main tank remains clean and aesthetically pleasing, while the biological filtration takes place in the refugium.

References

Fishkeeping {{Fishkeeping-stub

Construction

See also

References