Eartheaters are widespread throughout South America.  Five genera make up this group: Biotodoma ,from the Amazon and Orinoco watersheds and the coastal rivers of the Guyanas; Geophagus , widespread throughout four major rivers basins; Gymnogeophagus of the Rio Parana watershed; Retroculus , from the rapid rivers of French Guyanas and the lower Amazon; and Satanoperca of the Amazon and Orinoco watersheds, and Guyana.
SIZE : Eartheaters usually range in size from 6-12" (15-30 cm), although some species grow no larger than 4" (10 cm). 
TANK : Because of the wide range of size between Eartheaters, it is difficult to suggest a proper tank size. It is safe to say that for the larger species, the tank should measure at least 48" (122 cm) with a capacity of 55 gallons (209 L). Furnish the tank with a fine gravel or sand substrate as Eartheaters will sift through the bottom material. Use caves, roots, and wood for hiding places.  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.
WATER : Many species can accept a wide range of water conditions.  For practical purposes, only the general perimeters will be given: a pH from 6.5-7.5, a water hardness from 5-15 dH, and a temperature from 72-79°F(22-26°C).
SB : Eartheaters come in a wide range of dispositions.  Most are territorial, but many are peaceful,while others are aggressive and intolerant. See individual descriptions.
SC : 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 , and Doradids), characins (tetras, over 2.4," of the upper swimming levels; hatchetfish; pencilfish), cichlids (Angelfish,Severum, Festivum), and fish from other regions (Gouramis, Danios, Rasboras).  Larger Eartheaters can be combined with larger catfish (Pimelodids, Loricarids, Doradids), larger characins (Silver Dollars), and cichlids (Cichlasomines).  Bear in mind that Eartheaters practice brood care and are inhospitable towards other tank mates around spawning times.  Thus Eartheaters are best spawned in a tank of their own. 
FOOD : In nature, Eartheaters receive a fair part of their diet by sifting through the substrate.  In aquaria, they can be fed on such live foods as: worms, aquatic insects, insect larvae, and crustaceans.  Most will also accept flakes, tablets, and pellets.
B : Three major types of reproduction have been observed: substrate spawning, delayed (primitive) mouth brooding, and immediate (advanced) mouth brooding. 
(1) Substrate spawners ( Geophagus brasiliensis ) 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 there. 
(2)  Satanoperca leucostictus is an example of a delayed mouthbrooder, which lays its eggs on a flat surface and guarded by the female until the fry hatch. The fry are taken into the female's mouth where they are incubatedfor a period of two weeks. In this method the pair breaks up following the spawning. 
(3)  Geophagus steindachneri is an immediate mouthbrooder. After the eggs are fertilized, they are taken into the mouth of the female where they are incubated until the young can fend for themselves.  In this reproductive method, the males form harems and are strongly polygenic.
BP :  Eartheaters spawn in several different methods with a different degree of difficulty, thus one should see the individual descriptions for the rating on a particular species.
R : Eartheaters earned their common name by their habit of taking mouthfuls of substrate into their large, under-slung mouths. They do this in order to obtain food.  The substrate is filter through a part of the gill known as "rakers" where food is separated from debris.  The waste is passed through the gills and back into the water, leaving only the edible substance in the fish's mouth.
DIFFICULT OF CARE: See individual descriptions as to the degree of difficulty in care.
Cupid Cichlid
Biotodoma cupido
SYN : Acara subocularis, Geophagus cupido
PD : A cichlid with a rounded forehead and an elongated caudal peduncle.  The dorsal and pelvic fins are elongated, and the caudal fin is fan-shaped. Different color varieties exist.  A common variation has a gray back .  The flanks are marked with fine transverse stripes that may or may not be visible.  A black spot is located on the rear,upper-part of the fish. A black band runs through the eye from the forehead to the corner of the gill cover.  The coloration changes (depending on the angle of light) from orange to yellow to green to blue and finally, to purple as it nears the caudal fin. This rainbow of colors develop only in mature specimen that are kept in exceptionally maintained water. Young fish are dull gray. The dorsal fin is pinkish-red, while the anal fins is a dark violet. The tail may be grayish-green. The pelvic fin is turquoise in color.
SIZE : To 5.5" (14 cm), although usually smaller
SS : Biotodoma wavrini
HAB : Found is slow-moving, wide parts of clear rivers.  South America; Rio Tapajo near Santarèm(Brazil).
S: bottom, middle
TANK : A tank measuring 32" (81 cm) with a capacity of 30 gallons (114 L) is sufficient.  The foreground should include a fine gravel or sand substrate, and be open.  The background should include hiding places among thickets of hardy plants, roots, caves, and wood. 
WATER : pH 5-7 (6.5), dH 0-6 dH (2), 77-84°F (25-29°C).
SB : A territorial and somewhat aggressive fish that should be kept in pairs.  Problems with pairing are common, so allow a group of youngsters to pair off, and select the best pair.  This species should be kept with calm,small to medium-sized fish of the upper swimming levels.  Pairs form a nuclear family.
SC : Tetras, Headstanders, larger hatchetfish, Loricarids, Pimelodus , Armored catfish, dwarf Acaras
FOOD : Live; insect larvae, crustaceans, Tubifex ; flakes, pellets.
SEX: Males have blue iridescent lines on their cheeks, while females have spots.
B : Use water with a pH from 6.0-6.5, a water hardness of 0-4 dH, and a temperature from 81-84 F (27-29 C). The female will dig a pit with its mouth in the substrate.  The female lays about 100 eggs which are guarded by the male, with the female caring for the eggs.  When the are free-swimming about 10 days later,they can be fed rotifers and liquid foods. After another week or two, they are large enough to be given brine shrimp nauplii. The parents continue their care for the young.  The fry are difficult to raise.
BP : 8. Breeding is difficult.
R : Fish of the genus Biotodoma can be distinguished from other Geophagus ,by their smaller snouts and mouth. The Cupid Cichlid is sensitive to changes in water conditions and pollutants.  Wild-caught specimen are much more colorful, although they are also far more delicate.
DC : 6. A delicate species that may, at times be aggressive towards others of its own species.
Pearl Cichlid, Mother-of-Pearl Eartheater
"Geophagus" brasiliensis
SYN : Acarabrasiliensis, Chromis brasiliensis, Geophagus labiatus, G. obscura, G. pygmaeus
PD : A laterally compressed cichlid with a rounded forehead.  The anal, dorsal, and caudal fins are large when compared to those of other Eartheaters. The back is dark and the belly is salmon-pink.  The body color ranges from yellow to brown to dark red, and each scale is marked with a blue, green, or yellow spot.  The fins retain the scale pattern and coloring, except to have more blue and violet hues. The iris of the eye is golden with a black band running through it.  A lateral stripe, sometimes unnoticeable, runs from the eye to the base of the caudal fin.  Fish under 3" (8 cm) are an unattractive brown color.
SIZE : Males to 12" (30 cm) in nature, although no larger than 9" (23 cm) in captivity.  Females reach 6" (15 cm) in captivity.
SS : " Geophagus" gymnogenys
HAB : South America; found in the coastal rivers of Brazil.  This Eartheater is found along rocky banks of rivers that receive tidal influence.
S: bottom
TANK : A tank measuring 48" (122 cm) with a capacity of 55 gallons (209 L) is needed for adult sized fish. Use a substrate of fine gravel or sea sand-for buffering the pH.  The tank should be arranged with rock structures including caves. Only robust, potted plants should be used. 
WATER : pH 6.7-8.2 (7.3), 5-20 dH (11).  This species can tolerate a temperature as low as 50°F (10°C) for short periods of time, although it can be kept in a cool tropical set-up with temperatures from 66-75°F (18-24°C).
SB : A territorial, but peaceful species that is tolerant of other fish, including Eartheaters.  Combine with medium to large sized fishes. Pairs form monogamous bonds and nuclear families.
SC : Catfish ( Arius, Callichthys, Loricarids, Pimelodids, Doradids), characins (Silver Dollars, Headstanders), cichlids (Eartheaters, Cichlasomines).
FOOD : Live; Tubifex , crustaceans, snails, crabs; chopped meat; mussels; pellets; tablets.
SEX: Males develop nuchal humps on their forehead with age.  The male reaches a larger size and has a more elongated dorsal fin. The genital papilla of the male is pointed.
B : Use water with a pH from 6.5-7.2, a water hardness from 5-10 dH, and a temperature from 75-79°F (24-26°C). Condition the pair with nutritious live foods.  As many as 800 eggs are deposited on a previously cleaned surface that is usually hidden. The parents are fine parents which carefully care for the fry.  Start feeding with crushed dry foods and Artemia nauplii. The young grow quickly when fed often and kept in well-maintained water.  The eggs may be consumed in cases where a compatible pair is not found. 
BP : 6. Breeding is fairly easy.
R : A 0.5% addition of salt can be used.  This can be accomplished by adding 4 TSP. of salt per every 10 gallons (5 g of salt/10 L). 
DC : 4. A hardy fish recommended for the aquariast wanting to begin collecting Earth eaters.
Red hump Eartheater
"Geophagus" steindachneri
SYN : Geophagus hondae, G. magdalenae, G. pellegrini
PD : Males have a large, characteristic hump on their forehead that develops with age.  The body coloring differs depending on the population. Common colors are gold, green, red, orange, and black.  The body is marked with irregular black spots. The hump may change from golden to red.  The fins are spotted with iridescent scales. The male has an orange spot at each corner of his mouth.  These serve as the equivalent of the egg-spots of Lake Malawi Cichlids.
SIZE : To 10" in nature, although tank-bred fish usually do not exceed 6" (15 cm).  Females are considerably smaller.
SS : " Geophagus" surinamensis
HAB : South America; upper parts of the Rio Magdalena and its tributaries in Columbia and Venezuela.
S: bottom
TANK : A tank measuring 48" (122 cm) with a capacity of 50 gallons (190 L) is recommended for adult fish. Use a deep substrate of sand or fine gravel.  The back parts of the tank should be planted with large, well-rooted plants. Use wood, rocks, and caves for hiding places. 
WATER : pH 6.5-7.2 (7.1), 5-15 dH (8), 75-81°F (24-27°C)
SB : Females are not territorial, while dominant males can be aggressive.  This species can be combined with medium-sized fish of the upper swimming levels, and other Eartheaters.  Pairs may become aggressive during spawning season.  Keep one male with several females. Females perform matriarchal duties, while males often form harems. 
SC : Catfish (Loricarids, Pimelodids, Doradids), characins (Silver Dollars, Headstanders), cichlids (Eartheaters, Cichlasomines).
FOOD : Live; crustaceans, Tubifex , insects larvae; pellets; tablets; chopped meat.
SEX: Males are larger and more colorful with an egg spot at each corner of the mouth.  Males also have a characteristic hump on their forehead. 
B : Use the recommended water values and a temperature between 77-82°F (25-28°C).  Depending on the size of the female, from 30-150 bright yellow eggs are laid on a previously cleaned stone, following a brief courtship. The eggs are immediately taken into the female's mouth along with the sperm of a male.  The eggs are mouthbrooded for a period of 15-20 days. The female should not be fed during this time as she may accidentally swallow her brood. The large fry are easy to feed with dry and small live foods. 
BP : 6. Breeding is not difficult.
R : Several different coloration/geographical populations are known to exist.  Sexually mature from 2.8" (7 cm).
DC : 4. A robust and peaceful Eartheater.
Paraguay Mouthbrooder, Paraguay Eartheater, Balzanii
Gymnogeophagus balzanii
SYN : Geophagus balzanii
PD : An oval shaped fish with a tiny mouth.  Males develop an enormous hump on their forehead that extends from the front of the base of the dorsal fin, to the lips. The body coloring is generally light gray to brown on the upper flanks. The belly and the lower flanks are golden-yellow to chestnut brown.  Occasionally a few orange spots may be scattered on the hump, near the eye.  The fins are yellow to gold in color with some white spots on the edge of the anal, dorsal, and pelvic fins.  Females develop a dark spot and a stripe running from the eye to the cheek in their spawning dress. Some fish may have five to eight, vertical stripes on the body.  
SIZE : Males to 8" (20 cm), females to 5.5" (14 cm)
SS : None
HAB : Found in still and slow-moving swamps along rivers.  South America; Rio Paraguay, Rio Parana (Paraguay and Argentina).
S: bottom
TANK : A 48" (122 cm) tank with a volume of 55 gallons (209 L) is ideal for adult fish.  Use a sand or fine gravel substrate. Only robust, potted plants should be used as this fish is a burrower.  Leave some flat stones as this fish likes to rest on them. Provide hiding places with roots and wood.
WATER : pH 6.5-7.5 (7.0), 4-14 dH (8).  Although in nature, the Paraguay mouthbrooded can sometimes tolerate water temperatures as low as 59°F (15°C), it should be kept in water with a temperature from 70-77°F (21-25°C).
SB : A territorial, but peaceful and tolerant species that can be combined with other calmfish. Males form harems, so it is best to keep one with two or more females.  This species will not harm plants other that burrowing.
SC : Catfish (Loricarids, Pimelodids, Doradids, Armored Catfish), characins (Silver Dollars, Headstanders, larger tetras), cichlids ( Geophagus,Gymnogeophagus , Severum, Festivum).
FOOD : Live; snails, crustaceans, aquatic insects, insect larvae, Tubifex ; tablets.
SEX: At two inches (5 cm) males begin to develop their large nuchal humps that cover their entire forehead. Males are also larger and more colorful.
B : Use neutral water with a hardness from 8-12 dH, and a water temperature from 75-81°F(24-27°C). The female deposits up to 500 eggs on previously cleaned rocks.  The male fertilizes the eggs and then leaves. After 24-32 hours the larvae are sucked into the female's mouth, with the eggs shells being left behind. After the fry are released they can be fed with liquid foods and rotifers.  Later they can be raised on brine shrimp and Cyclops nauplii. The fry retreat into the mother's mouth at times of danger.  The fry are slow-growing and difficult to raise. 
BP : 7. Breeding is moderately difficult although the fry are difficult to rear.
R : Do not keep the Paraguay Mouthbrooder at too warm a temperature as it causes the fish to become more sensitive. The water must be well-maintained with frequent partial water changes as this cichlid is very sensitive to the build-up of toxic compounds. When water qualities decline, the fish are susceptible to hole-in-the-head disease. Sexual maturity is reached at the age of one year when fish measure about 2.3" (6 cm).  Eight species belong to the genus Gymnogeophagus or "Naked Eartheater" group.  Nearly all fish available to the hobby are captive bred.
DC : 6. A sensitive species who characteristic hump makes it quite interesting.
Demon Fish, 'Jurupari,' Eartheater
Satanoperca leucosticta
SYN : Geophagus jurupari, G. leucostictus, Satanoperca jurupari, S. leucostictus
PD : An elongated, laterally compressed cichlid with a large, rounded head.  Each ray of the dorsal fins comes to a shape point. The body color is greenish-yellow to yellow-brown with each scale having an iridescent yellow to gold spot. On the head, these spots may develop a turquoise blue iridescence.  The fins retain a similar pattern as the body. Sometimes faint, broad transverse stripes are present on the body.
SIZE : To 12" (30 cm), although not usually larger than 9" (23 cm) in aquaria
SS : Other Satanoperca species
HAB : South America; Brazil and Guyana.
S: bottom, middle
TANK : A tank measuring 48" (122 cm) with a capacity of 55 gallons (209 L) is sufficient for adult fish. Use a fine gravel or sand bottom.  The tank should include hardy plants, roots,wood, and rocks for hiding places. Use an efficient filtration system as the substrate is stirred up from constant burrowing. This species favors peat filtration.
WATER : pH 6.2-7.5 (6.9), 3-15 dH (8), 77-84°F (25-29°C)
SB : A peaceful and non-aggressive cichlid.  This Demon Fish is the most peaceful of the genus Satanoperca . Combine with other Eartheaters, catfish, and smaller fish of the upper swimming levels.  This cichlid may not spawn with other species are present as the presence of other fish tends to intimidate them.  Pairs form nuclear families.
SC : Catfish ( Callichthys, Loricarids, Pimelodids, Doradids), characins (Hatchetfish, Headstanders,large tetras), cichlids (Eartheaters).
FOOD : Live; Tubifex , crustaceans; tablets; sinking flake foods.
SEX: Males are slightly larger and more slender with maturity.
B : Use a separate breeding tank with the following range of water values: pH 6.2-7.0, 5-10dH, 81-86°F (27-30°C). Up to 400 eggs are laid on a previously cleaned stone.  These eggs are tended to and guarded for a period of 24-30 hours, when they are taken into the mouth of the female.  Over the course of two weeks, the mouthbrooding duties are evenly shared between the two parents.  The fry are held in the front of the mouth, not in the throat sac like many other species. After two weeks, when the fry are free-swimming, they are released.  Start feeding with Artemia nauplii. The fry seek shelter in the parent's mouth at times of danger.  Remove the fry after a period of three to four weeks. The young grow slowly.
BP : 7. Breeding is moderately difficult to induce, and the fry are not easy to raise.
R : This species is often sold under the name S. jurupari , although S. jurupari is a separate, seldom imported,species. The name Satanoperca is Latin for 'Satan's Perch.' Jurupari is taken from the Tupi Indian word meaning 'demon's lure,' after a relationship drawn between this species and the forest demon mentioned in local folklore.
DC : 5. A hardy and peaceful Eartheater that is sensitive to cool water.