Amazon River: South American Cichlids – Acaras, Dwarf and Eartheaters

Amazon River: South American Cichlids – Acaras, Dwarf and Eartheaters

GENERAL INFORMATION: About the Amazon River

With a length of around 10, 600 kilometres (which is roughly the same as a round trip from Brisbane to Melbourne – 5 times), the Amazon River is the second longest river in the world – second only to the Nile in Africa. The drainage basin of this river is the largest in the world.

The network of rivers that drain into it extends over most of South America. The Amazon contains more water than any other river and in one second pours more than 600 000 cubic metres of freshwater into the Atlantic Ocean – diluting the salt of the ocean for a distance of 260 kilometres from the shore (a return trip from Brisbane to Noosa).

The river starts as a trickle in the Andes Mountains of Peru and runs through Brazil to the Atlantic Ocean. The massive amounts of silt deposited at the mouth of the Amazon each year have created the largest river island in the world – Marajo Island.

The Amazon Basin was formed between 500 and 200 million years ago. Today, the Andes and the Amazon jungle are home to more than half the world’s known flora and fauna.

It may be of interest to you:

A Selection of Natural Habitats (Biotopes)


  • The Amazon River makes up about one-fifth of the Earth’s freshwater.
  • Each year the Amazon deposits tonnes of sediment into the Atlantic Ocean.
  • The Amazon is the widest river in the world. Many kilometres from its mouth it can be as wide as 11 kilometres and up to 40 kilometres in the wet season.
  • Where it meets the Atlantic Ocean it spreads to cover some 325 kilometres.
  • The Amazon was named by Spanish explorers. Female warriors called Icamiabas (women without husbands) attacked Francisco Orellana and he named the river Rio Amazonas after these women – who he compared to the legendary Amazons of ancient Greek mythology.
  • The Amazon Basin and its surrounding rainforests and plains are home to many different animals.
  • The Amazon River itself is home to over 2000 species of fish – more species than are in the Atlantic Ocean.
South American habitats

South American habitats

South America consists of three major water types: whitewater, clearwater, and blackwater.

Whitewater rivers

Whitewater rivers are a dirty white colour. They get their name and colour from the clay silt that is suspended in the water.

  • This clay silt – continually eroded from, and deposited on, the clay river banks – mean that whitewater rivers are rich in nutrients.
  • There are few submerged plants as light cannot penetrate the cloudy waters effectively. In still places whitewater does support abundant floating plants.
  • The fish living in these environments survive mainly on food that falls from the trees growing along the banks.
  • Whitewater parameters are: pH 6.8-7.1 and hardness 3-5 dH.
  • The best-known whitewater river is the Amazon River.

Clearwater rivers

Clearwater rivers are tributaries which flow through ancient Brazilian and Guyana rock beds. There is little sediment released into these rivers.

  • The waters are very clear although there may be a slight greenish tint due to suspended algae.
  • They have by far the pH widest range of any South American water type.
  • Like blackwater, clearwater is generally quite nutrient poor and often is found over a sandy bottom.
  • Clear water rivers have: pH 5.0-7.8 and hardness between 5 and 12dH.

The Rio Xingu and the Rio Tocantins are examples of clearwater rivers.

Blackwater rivers

Blackwater rivers are nutrient poor and stained with tannins from decaying vegetation – giving them a tea-coloured appearance.

  • Blackwater rivers are crystal clear and contain no dissolved minerals.
  • This water does not support much life as it generally has a low oxygen content, although some of the shallower streams and ponds are home to Dwarf Cichlids such as Apistogramma.
  • Blackwater is typically found above white, acid sands.
  • Blackwater rivers are: acidic (6.0 pH) and soft, with little measurable water hardness (0 dH).

The Rio Negro is the most famous of the blackwater rivers.

There are also waters which fit none of the three main types mentioned above. These include coastal rivers and lagoons which are harder and brackish, and mud-bottomed swamps.

The Fish

There are estimates of over 300 species of cichlids that are found throughout the waters of South America. An estimated 75 percent of these inhabit the Amazon River Basin.

However, cichlids are not the most abundant fish in this river. They make up only around 10 percent of all fish species found there.

Among South American Cichlids are the well-known Angelfish, Discus, and Oscar. Others include the Acaras, Dwarf Cichlids and Eartheaters.

South American Cichlids differ greatly from one another in body shape, colouration, and survival habits. The range in size from the Dwarf Cichlids such as the popular Ram through to the giant Peacock Bass, regarded by many fishermen as the ultimate sport fish.

Acara-type Cichlids

Acara-type Cichlids

The name Acara is a native South American Indian – Guarani – word and is used to describe the South American cichlids which have an «egg-shaped» body.

The word Acara means fish of little worth. The Acara group includes fish of the genera Aequidens, Cleithracara, Laetacara and Nannacara. Two of the better known Acara-type cichlids are the dwarf Keyhole Cichlid and the Green Terror. The Acara Family is found only in tropical South America.


The Acara group contains true dwarf cichlids such as Cleithracara and Nannacara, which typically stay under 8 centimetres in size, up to to the largest and most aggressive of the group – Aequidens rivulatus – which reaches about 20 centimetres.

Acaras all share the same body shape that characterises this group. They are stocky fish, egg-shaped or oval fish. They don’t have a high body like many of the other South American cichlids, particularly the Cichlasomines.

Most Acaras were originally classified under the genus Aequidens, but many have since been assigned new scientific names.

Tank care

Acaras are found in all water types and most are able to adapt to a wide range of water parameters in captivity.

Some species, particularly the dwarf species, may be sensitive to water parameters too far outside their natural range, so it is advisable to keep most species in conditions close to those in which they are found in nature.

If you are unsure of the water type in the natural habitat of a particular species, a good rule of thumb to follow is to assume that brightly coloured and/or heavily patterned species are blackwater or clearwater species and less colourful species are from whitewaters.

This is because, in whitewater there is little need for bright colours or patterns as the low visibility prevents them from being used for species recognition or mate selection. In waters with high visibility, the bright colours and patterns of the males are used to attract females.

Regardless of the water conditions, Acaras are most often found in calm waters.

  • Smaller Acara-related species can kept in a 60 centimetre tank, while the larger types in an 80 centimetre tank. These Acaras will not uproot or eat plants.
  • The larger Acaras (Aequidens) need a tank measuring at least 100 centimetres. These Acaras have a tendency to uproot plants, so only large, robust types should be used.
  • All Acaras prefer large open swimming areas. Retreats, created by using wood, roots, and rocks, are necessary.


Most Acaras are generalised omnivores. This means that they do not need a specialised diet for successful keeping. A staple diet of pelleted food or floating food sticks works just fine for most Acaras.

In addition to flake or pellet foods, which most Acaras will take greedily, quality frozen and live foods are recommended, especially to get the fish into breeding condition. Frozen bloodworm, chopped earth worms and live black worms are all eaten with relish.


Acaras, with notable exception of Green Terrors, tend to be relatively peaceful, non-aggressive fish. Some, such as Keyhole Cichlids can be quite timid if kept with larger more boisterous fish.

Most Acaras can be successfully mixed with other cichlids of similar size and temperament, with catfish such as Corydoras, loricariids (sucker-mouthed catfish), Synodontis and Pimelodids and peaceful characins (such as Tetras or Silver Dollars).

There are some reports that Nannacara anomala can kill catfish of the genus Corydoras, but Corys can be successfully mixed with the other dwarf Acaras – of the genus Cleithracara and Laetacara.

Dither fish, such as schooling fish including Tetras, Danios and Rainbowfish, can help to diffuse aggression or help shy dwarf species to feel less threatened. This will make them more active in the tank, as when they see other fish swimming around they know it’s safe.


Most Acaras are quite easy to spawn in the aquarium. This, and the fact that they are generally excellent parents, makes them a good choice for first time cichlid breeders.

Most Acaras are biparental substrate spawners with all parental duties shared – although males often spend more time defending the territory and females spend more time caring for the eggs and fry.

They select a sheltered, smooth, horizontal surface, like a flat rock, and clean it before they females lays between 100 to several hundred eggs.

Both parents look after the fry when they hatch. Acaras use pits to move their fry from place to place before they become free-swimming.

Acara-type species

  • Aequidens portelagrensis (Port Cichlid)
  • Aequidens pulcher (Blue Acara)
  • Aequidens rivulatus (Green Terror)
  • Cleithracara maronii (Keyhole Cichlid)
  • Laetacara curviceps (Curviceps)
  • Nannacara anomola (Golden Dwarf Cichlid)

Dwarf Cichlids

Dwarf Cichlids


Usually measuring no more than around 11 centimetres, Dwarf Cichlids can be found in small streams and oxbow lakes throughout tropical South America. The largest group of Dwarf Cichlids are in the genus Apistogramma – which contains over 50 species.

Other fish that can be classified as Dwarf are in the genera Dicrossus and Mikrogeophagus (as well as Cleithracara, Laetacara and Nannacara mentioned in the Acara-type section).

Apistogramma species and Mikrogeophagus species are classed as Geophagines (Eartheaters). Dicrossus species belong to the Crenicarines, which share many features with the Geophagines and are closely related.

Tank care

Most Dwarf Cichlids are content in a tank measuring 60 centimetres, although some species require more space. Since these cichlids often inhabit overgrown, rainforest streams and lakes, heavy vegetation should be included in the tank.

In the wild, many of these fish can be found living under the build up of leaf litter on the bottom of the stream, where they hide from predators.

The tank should have plenty of hiding places using small forests of plants, rocks, roots, and wood.

The more hiding places that are provided, the more secure the fish will feel – and the more they will swim around the tank. The lighting should be dim and there should be a partial cover of floating plants because these species frequently live in shaded areas.

The filter should create little water disturbance. Leave open swimming areas and use a dark substrate. The majority of Dwarf Cichlids demand very good water quality. It is important that the water is very clean and exceptionally low in nitrates, so regular partial water changes are important. Dwarf Cichlids prefer fairly soft, slightly acidic water.

Many Dwarf Cichlids are also sensitive to medications, so care is needed if medication is required: using a reduced dose of the gentlest medication available is recommended. Many species prefer peat filtration, which keeps the water soft and acidic.


Dwarf Cichlids are shy and peaceful. Each fish will establish a favorite spot (cave, overturned flowerpot) and will defend it against other fish. Dwarf Cichlids can be combined with each other, with peaceful schooling fish of the upper swimming levels and with small peaceful catfish and Loaches.

However, around spawning time, catfish should be removed as some Dwarf species have been observed picking out the eyes of the catfish in their efforts to protect their brood. All Dwarf Cichlids are plant-friendly and well suited to planted tanks.


Dwarf Cichlids require a varied diet including live foods in order to thrive. Livefoods such as Brine Shrimp, mosquito larvae, black worms can be fed, as well as brozen bloodworms or brine shrimp.

Good quality tropical flake is generally best as a staple.


Apistogramma species are secretive substrate spawners, with the female usually laying her eggs on the ceiling of a cave – an overturned flowerpot or under a log will suit. Crevices between rocks may sometimes be used if no suitable cave is present.

Other Dwarf Cichlids are substrate spawners, laying their eggs on plant leaves or stones, or in pits dug in the gravel. Apistogramma species and Dicrossus are usually harem spawners, while Mikrogeophagus form pair bonds – although some Apistogramma will also spawn in pairs.

In all species, except Mikrogeophagus, the female takes care of the brood while the male defends the territory. Rams (both Mikrogeophagus species) form families with both male and female sharing the role of defending the eggs and fry.

Dwarf Cichlid species

  • Apistogramma borelli (Yellow Dwarf Cichlid)
  • Apistogramma cacatuoides (Cockatoo Cichlid)
  • Apistogramma nijsseni
  • Apistogramma pandurini
  • Dicrossus filamentosa (Checkerboard Cichlid)
  • Mikrogeophagus altispinosa (Bolivian Ram)
  • Mikrogeophagus ramirezi (Ram)

Eartheaters (Geophagine)

Eartheaters (Geophagine)

The large Geophagines – Eartheaters – are widespread throughout South America. Four of the six genera making up this group are available in Queensland:

  • Acarichthys;
  • Geophagus, which are widespread throughout four major rivers basins;
  • Gymnogeophagus, found in the Rio Parana watershed;
  • Satanoperca from Guyana and the watersheds of the Amazon and Orinoco Rivers.


Eartheaters are the most specialised of the South American cichlids in their feeding habit and show the adaptions of their «earth eating» nature by having a relatively elongated nose with a sloping forehead profile.

In most species the eyes are also quite high on the head to protect them when the fish digs in the substrate. These species were all formerly classified in the genus Geophagus.

Eartheaters get their common name because of their habit of taking mouthfuls of substrate into their large, under-slung mouths as they search for food.

The substrate is filtered through gill rakers, where any food is separated from debris. The waste is passed through the gills and back into the water, leaving only the food in their mouth. Eartheaters usually range in size from 15-30 centimetres (excluding the Dwarf Geophagines).

Tank care

Eartheaters are relatively undemanding of exact water quality values, prefering a pH of around neutral and moderate hardness. Good filtration is recommended as they do tend to stir up the substrate.

They need a fine gravel or rounded pebble substrate, as they may otherwise injure themselves trying to take coarse or rough gravel into their mouths. Live plants can be used, although they should be potted and robust. Leave open swimming areas and open patches of sand.

Flat stones can serve as potential spawning sites. For the larger species, the tank should measure at least 120 centimetres. Many species can accept a wide range of water conditions, but the water quality must be good.

If the water quality is allowed to deteriorate, many Eartheaters can suffer from Hole-in-the-Head Disease.


Eartheaters come in a wide range of dispositions. Most are territorial, but many are peaceful, while others are aggressive and intolerant. Eartheaters can be combined with a wide range of other species, depending on the species of Eartheater.

Suitable tank mates for smaller Eartheaters include:

  • catfish (Loricarids, Corydoras, Brochis and Doradids);
  • characins (tetras; hatchetfish; pencilfish);
  • other cichlids of the same temperament, such as Angelfish
  • fish from other regions (Gouramis, Danios, Rasboras and Rainbowfish).

Larger Eartheaters can be combined with:

  • larger catfish (Pimelodids, larger Callichthids (Hoplos and Dianemas), Loricarids, Doradids);
  • larger characins (Silver Dollars);
  • larger robust anabantids
  • other cichlids (Cichlasomines).


In their natural environment, Eartheaters get most of their food by sifting through the substrate. In the tank, they can be fed on such live foods such as earthworms and black worms. Most will also accept flakes, tablets, and pellets.


In Eartheaters, three main types of reproduction are found:

  • substrate spawning;
  • delayed (primitive) mouth brooding and
  • immediate (advanced) mouth brooding.

Substrate spawners (Geophagus brasiliensis), like other substrate-spawning cichlids, lay their eggs on a flat stone or piece of wood that is located out in the open. The parents guard the eggs and the fry.

Delayed mouthbrooder (Satanoperca leucostictus) lay their eggs on a flat surface and the female guards the eggs until the fry hatch. The wrigglers are taken into the female’s mouth where they are incubated for about two weeks. In this method the pair breaks up following the spawning.

Immediate mouthbrooder (Geophagus steindachneri) is when the female takes the eggs into her mouth immediately after they are laid and fertilised – similar to the African mouthbrooders. She incubates them until the young can fend for themselves. In this reproductive method, the males form harems and are strongly polygamous.

Eartheater species

  • Acarichthys heckelii (Thread-fin Acara)
  • Geophagus altifrons Tocantins
  • Geophagus brasiliensis
  • Geophagus dicrozostus
  • Geophagus sp Pindare
  • Geophagus steindachneri (Red Hump Cichlid)
  • Geophagus surinamensis (Red Horseface)
  • Gymnogeophagus balzanii
  • Satanoperca leucosticta (Jurupari)
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