Choosing brackish water fishes involves all the same
considerations as choosing freshwater or marine fishes, plus one
additional factor: salinity. Broadly speaking, brackish water fishes
divide up into species that are essentially freshwater fish with some
tolerance of salt, marine fish that tolerate reduced salinity, and
truly euryhaline fishes that are happy across a wide range of
salinities. An example of a salt-tolerant freshwater fish is the common
krib, Pelvicachromis pulcher. It is ideally kept in freshwater,
but will also do well in slightly brackish water. On the other hand, it
cannot be kept in moderately or strongly brackish water. Many marine
fishes enter brackish water to spawn and consequently mangroves and
estuaries are often called the "nurseries of the sea" by
marine biologists. The dog-faced puffer Arothron hispidus is an
example of a marine fish that spawns in brackish water and juveniles
are very common in estuaries. Many marine fishes will also make forays
into brackish water to feed, taking advantage of the relative abundance
of food in estuarine habitats. Finally, there are those fishes that are
able to quickly adapt to changes in salinity and are able to move
freely between freshwater habitats and the sea. Of the species kept by
aquarists, the common scat Scatophagus argus is the best known
example, and in the wild it spends its entire life in coastal waters
making periodic forays into rivers and sometimes being found dozens of
miles inland, well into the freshwater zone.
Although less often discussed, brackish waters are
teeming with invertebrates as well, ranging from insects and insect
larvae through to large molluscs and crustaceans. Crabs, hermit crabs,
shrimps, oysters, clams, mussels, and marine snails of various types
are all classic brackish water invertebrates, although insects,
particularly mosquitoes, are also very important parts of many brackish
water invertebrate faunas. In fact, mid to high salinity brackish
waters often contain much the same variety and density of invertebrates
as marine waters, with a few notable differences; for whatever reason,
echinoderms, anemones, corals, barnacles, and cephalopods are rarely
seen in brackish waters. For this reason, the aquarist trying to create
an authentic brackish water habitat should certainly consider adding
some oyster or mussel shells to his aquarium, but bleached corals and
barnacle shells would be much less appropriate except perhaps as
pulverised rubble on the substrate.
Planting the brackish water aquarium is problematical
because apart from mangroves, higher plants are not really a key
feature of most brackish water habitats. By the time a river reaches
the sea, it is usually heavy with sediment, and few plants thrive in
such murky water. Mangroves grow above the waterline of course, so they
aren't bothered by this, and in fact the sediment gets trapped
around their roots and forms an excellent, nutrient-rich substrate.
Along the edges of the estuary where the water is shallow, plants may
be found, but large algae, particularly brown algae, are much more
characteristic. Brown algae generally do not do well in aquaria, and
are best replicated using plastic alternatives. Among the plants that
inhabit brackish waters, a few are traded commercially, most notable
Java ferns, Java moss, Bacopa monnieri, Crinum
calamistratum and Crinum pedunculatum, Cryptocoryne
ciliata, Lilaeopsis brasiliensis, and Samolus
valerandi. These will happily take a specific gravity of around
1.005 if acclimated carefully, and some species will accept
significantly higher salinities after adaptation. At lower salinities
(SG 1.003 or less), most hard water tolerant plants will do acceptably
well if other factors such as lighting and nutrients are good,
including Amazon swords, Hygrophila spp., and Vallisneria
spp.
The small, low-salinity brackish water aquarium
For the aquarist with limited space, a low salinity
aquarium, planted or otherwise, is a worthwhile option. A typical low
salinity brackish water environment would be a coastal stream thick
with plants, where the influence of the sea is only very slight. There
are many small brackish water fishes, in particular gobies,
livebearers, killifish, glassfish, halfbeaks, pufferfish, and dwarf
cichlids that would work well in an aquarium based around this
environment. Some of these will do well even in tanks as small as 10
gallons. A low salinity aquarium should be maintained at SG
1.003-1.005, the exact salinity depending on which fish and plants
being kept.
Colourful or interesting species for the small
(10-30 gallon) low salinity aquarium include:
|
Common name
|
Latin name
|
Comments
|
|
Guppy
|
Poecilia reticulata
|
Doesn't need salt, but has a high salt
tolerance.
|
|
Endler guppy
|
Poecilia wingei
|
Doesn't need salt, but has a high salt
tolerance.
|
|
Dwarf mosquitofish
|
Heterandria formosa
|
Very small, lively fish best mixed with other small
species, such as gobies.
|
|
Common mosquitofish
|
Gambusia affinis
|
Aggressive, very hardy, but for a single species
aquarium only.
|
|
Fancy mollies
|
Poecilia
hybrids
|
All do very well in brackish water, but need tanks
20 gallons or bigger.
|
|
Banded lampeye
|
Aplocheilichthys
spilauchen
|
Very peaceful little fish, ideal for use with
gobies in a planted aquarium.
|
|
Florida flagfish
|
Jordanella floridae
|
Mildly aggressive towards its own kind; an
excellent algae-eater, needs greens in its diet.
|
|
Wrestling halfbeaks
|
Dermogenys
spp.
|
Males fight among themselves; relatively easy to
keep and breed by halfbeak standards.
|
|
African pipefish
|
Microphis "smithi"
|
Difficult; needs lots of live food; best in a
single-species aquarium with lots of plants.
|
|
Orange chromides
|
Etroplus maculatus
|
Territorial when breeding, but otherwise
unproblematic and very attractive.
|
|
Kribensis
|
Pelvicachromis pulcher
|
Optimal breeding conditions are at pH 7.0, but
otherwise thrives in brackish water.
|
|
Butterfly-goby waspfish
|
Neovespicula depressifrons
|
Very grouper-like (including ability to swallow
smaller tankmates); otherwise easy to keep.
|
|
Asian freshwater flatfish
|
Brachirus spp.
|
Nocturnal, feed on bloodworms and other small
animals; easily starve in busy tanks.
|
|
Bumblebee goby
|
Brachygobius
spp.
|
Beautiful, active, territorial little fishes;
superb in planted aquaria.
|
|
Rhinohorn goby
|
Redigobius balteatus
|
Similar to bumblebee gobies in terms of care, but
less often seen.
|
|
Spaghetti eel
|
Moringua raitaborua
|
A scaled-down moray eel; feeds on worms and insect
larvae; nocturnal; likes to burrow.
|
|
Peacock spiny eel
|
Macrognathus siamensis
|
Needs sand for digging; sociable; nocturnal;
quickly escapes from uncovered aquaria.
|
|
Glassfish
|
Parambassis ranga
|
Lively, like to chase one another, so keep in
groups! Prefers live/frozen foods, rarely eats flake.
|
|
Figure-8 puffer
|
Tetraodon biocellatus
|
Very entertaining; best kept alone or in groups
(10-15 gallons per pufferfish).
|
|
Red-nose shrimp
|
Caridina gracilirostris
|
Does better in brackish water than fresh; easy to
keep.
|
|
Amano shrimp
|
Caridina multidentata
|
A freshwater species that will do well at a low
salinity.
|
|
Olive nerite
|
Vitta usnea
|
Does much better in brackish water than fresh;
excellent algae eater.
|
|
Colombian ramshorn
|
Marisa cornuarietis
|
Tolerates brackish water, but doesn't need
salt; destroys plants.
|
|
Malayan livebearing snail
|
Melanoides tuberculata
|
Does very well in brackish water; excellent for
keeping sand clean; eats some algae.
|
A medium-sized, moderately brackish water aquarium
In an aquarium around 30-55 gallons in size it becomes
possible to keep some of the more interesting oddball brackish water
fishes. Many of these are euryhaline species that can adapt to a range
of salinities, but a moderate salinity between 1.005-1.010 would work
well for most of the species listed below. Moderately brackish water
habitats tend to lack aquatic plants except mangroves, and so the
aquarist would find decorating the tank with sand, rocks, wood, and
shells much more true to life (as well as easier to do). Adding peat
granulate to the filter (or blackwater extract to the water) is a great
way to create the dark water conditions most of these fish enjoy, but
keep a close eye on the pH, as this should be maintained around 7.5 to
8.0.
Colourful or interesting species for a medium-szied,
medium salinity aquarium include:
|
Common name
|
Latin name
|
Comments
|
|
Fancy mollies
|
Poecilia
hybrids
|
Lively and colourful, but don't keep with
aggressive or predatory tankmates
|
|
Sailfin molly
|
Poecilia latipinna
|
Best kept in large schools, as the males can be
aggressive.
|
|
Giant sailfin molly
|
Poecilia velifera
|
Rarely seen, larger version of the sailfin
molly.
|
|
River halfbeaks
|
Zenarchopterus
spp.
|
Large size (~6") demands a wide, broad tank,
depth immaterial; nervous, keep with gentle tankmates.
|
|
Four-eyed fish
|
Anableps spp.
|
Not easy to keep, but fascinating fish for the
single-species aquarium.
|
|
False anableps
|
Rhinomugil corsula
|
An Asian mullet; nervous, schooling fish, but hardy
and not too big (~6" in aquaria).
|
|
Grunting toadfish
|
Allenobatrachus grunniens
|
Up to 12"; pretty inactive; predatory but
otherwise peaceful.
|
|
Hogchoker sole
|
Trinectes maculatus
|
Typically 6" or so; nocturnal; prefers live
foods, especially worms.
|
|
Oriental sole
|
Brachirus orientalis
|
Up to 8"; nocturnal; hardy; eats most live and
frozen foods.
|
|
Mudskippers
|
Periophthalmus
spp.
|
Most are 3-6"; territorial; hardy; need land
and humid air; only use water for "dipping".
|
|
Violet goby
|
Gobioides spp.
|
Around 10-15"; territorial; need sand for
digging; filter feeders, also need some algae.
|
|
Clay goby
|
Dormitator lebretonis
|
Midwater goby; territorial; omnivorous; will eat
small tankmates.
|
|
Knight goby
|
Stigmatogobius sadanundio
|
Midwater goby; territorial; predatory; will eat
small tankmates.
|
|
Sleeper goby
|
Eleotris spp.
|
Around 6"; territorial; predatory; will
eat small tankmates.
|
|
Crazy fish
|
Butis butis
|
Around 6"; territorial; predatory; will
eat small tankmates.
|
|
Moray eel
|
Gymnothorax tile
|
Up to 2', so keep in a 40-55 gallon tank;
predatory, best kept in groups, in a single-species tank.
|
|
Green spotted puffer
|
Tetraodon nigroviridis
|
Around 5-6"; territorial, best kept alone.
|
|
Topaz puffer
|
Tetraodon fluviatilis
|
Around 5-6"; territorial, best kept alone.
|
|
Freshwater archer
|
Toxotes microlepis
|
Prefers SG 1.005 or less, but small size
(4-5") makes it an attractive subject for home aquaria.
|
|
Papuan scat
|
Selenotoca papuensis
|
Rarely traded, but small size (around 4")
makes it a highly attractive species.
|
|
Orange mono
|
Monodactylus kottelati
|
Sometimes mixed with common monos; much smaller
than other monos (less than 4").
|
|
Olive nerite
|
Vitta usnea
|
Other nerites work well too, e.g., Puperita
pupa and Neritina virginea.
|
|
Red-claw crab
|
Sesarma bidens
|
Amphibious, need similar aquarium to
mudskippers.
|
|
Fiddler crabs
|
Uca spp.
|
Amphibious, need similar aquarium to
mudskippers.
|
A large, high salinity brackish water aquarium
Aquarists with 100-200 gallon tanks at their disposal
have some excellent species to choose from, including many of the more
spectacular and attractive brackish water fish. In a high salinity
aquarium a protein skimmer will work well. For all these fish, a high
pH and hardness is important, so adding a calcareous substrate in the
aquarium as well as using calcareous rocks for decoration can be very
helpful. Many of these fishes are predatory, or at least opportunistic,
so mix species of similar size. Catfish and archerfish in particular
are easily underestimated as piscivores! Some of these are schooling
fish, in which case keep in groups of six or more for best effect.
Blue-legged hermit crabs are excellent scavengers, while nerite snails
are superb algae eaters, some species even eating diatoms and
blue-green algae. Pufferfish will, of course, eat both hermits and
nerites given the chance.
Colourful or interesting species for a big, high
salinity salinity aquarium include:
|
Common name
|
Latin name
|
Comments
|
|
Sailfin molly
|
Poecilia latipinna
|
Best kept in large schools, as the males can be
aggressive.
|
|
Giant sailfin molly
|
Poecilia velifera
|
Rarely seen, larger version of the sailfin
molly.
|
|
River halfbeaks
|
Zenarchopterus
spp.
|
Large size (~6") demands a wide, broad tank,
depth immaterial; nervous, keep with gentle tankmates.
|
|
Grunting toadfish
|
Allenobatrachus grunniens
|
Up to 12"; pretty inactive; predatory but
otherwise peaceful.
|
|
Hogchoker sole
|
Trinectes maculatus
|
Typically 6" or so; nocturnal; prefers live
foods, especially worms.
|
|
Oriental sole
|
Brachirus orientalis
|
Up to 8"; nocturnal; hardy; eats most live and
frozen foods.
|
|
Spotted sleeper
|
Dormitator maculatus
|
Big (12") goby; territorial; easily tamed;
omnivorous; will eat small tankmates.
|
|
Estuarine bagrid
|
Mystus gulio
|
Around 12"; schooling fish; peaceful but
predatory.
|
|
Eel catfish
|
Plotosus lineatus
|
Around 12"; territorial when mature, schooling
when young. Venomous: handle with care.
|
|
Shark catfish
|
Hexanematichthys seemanni
|
Around 10-12" in aquaria; very peaceful
schooling fish, but predatory; beautiful!
|
|
Moray eel
|
Gymnothorax tile
|
Up to 2', so keep in a 40-55 gallon tank;
predatory, best kept in groups, in a single-species tank.
|
|
Black-chin tilapia
|
Sarotherodon melanotheron
|
Territorial; omnivorous; paternal mouthbrooder.
|
|
Maya cichlid
|
Cichlasoma urophthalmus
|
Territorial; big; an attractive euryhaline
cichlid.
|
|
Green chromide
|
Etroplus suratensis
|
Schooling vegetarian; prefers moderate SG, no
higher than 1.012.
|
|
Dog-face puffer
|
Arothron hispidus
|
Keep at SG 1.012 or more; very hardy, and
relatively peaceful (for a puffer).
|
|
Topaz puffer
|
Tetraodon fluviatilis
|
Around 5-6"; territorial, best kept alone.
|
|
Green spotted puffer
|
Tetraodon nigroviridis
|
Around 5-6"; territorial, best kept alone.
|
|
Targetfish
|
Terapon jarbua
|
Peaceful schooling fish when mature, but juveniles
territorial; up to 6" in captivity.
|
|
Common archer
|
Toxotes jaculatrix
|
Big, around 6-8" in aquaria, but 10"+ in
the wild. Territorial, often squabbles with conspecifics.
|
|
Common scat
|
Scatophagus argus
|
Big, messy, but loveable fish. Peaceful and easy to
keep, but watch water quality.
|
|
Common mono
|
Monodactylus argenteus
|
Reach 4-6" in aquaria; needs lots of swimming
space; best kept in groups of 6 or more.
|
|
Olive nerite
|
Vitta usnea
|
Other nerites work well too, e.g., Puperita
pupa and Neritina virginea.
|
|
Blue-legged hermit
|
Clibanarius tricolor
|
Hardy, easy to keep algae eater; SG 1.010 upwards.
Good with monos, scats, etc.
|
|
Mangrove horseshoe
|
Carcinoscorpius rotundicauda
|
Difficult to keep; needs sandy substrate, lots of
fine food, plenty of space.
|
|
|
