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Cichlids / South America / Eartheaters / Paraguay Mouthbrooder

Paraguay Mouthbrooder, Paraguay Eartheater, Balzanii
Gymnogeophagus balzanii

Synonyms: Geophagus balzanii
Physical description: 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/Length: Males to 8" (20 cm), females to 5.5" (14 cm)
Similar species: None
Habitat: Found in still and slow-moving swamps along rivers.   South America; Rio Paraguay, Rio Parana (Paraguay and Argentina).
S: bottom
Aquarium: 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 chemistry: 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).
Social behavior: A territorial, but peaceful and tolerant species that can be combined with other calm fish.  Males form harems, so it is best to keep one with two or more females.   This species will not harm plants other that burrowing.
Suggested companions: 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.
Breeding techniques: 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 roftiers.   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. 
Breeding potential: 7.  Breeding is moderately difficult although the fry are difficult to rear.
Remarks:  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.
Difficulty of care: 6.  A sensitive species who characteristic hump makes it quite interesting.


By Rhett Butler   Mongabay.com