Care
The Paraguay Eartheater is known from the Rio Paraná basin in Argentina, Brazil, and Paraguay, and also from the Rio Uruguay drainage in Brazil and Uruguay. Here it is most commonly encountered in calm pools and backwaters, away from the main river channels. The aquarium should be biologically mature and spacious, with a large expanse of soft sand substrate as these fish like to sift through the substrate in their ongoing search for food items. Provide plenty of hiding places amongst tangles of driftwood, rocky caves, and robust planting cultivated on the wood (such as Anubias sp. or Java Fern). Vegetation planted into the substrate is likely to be dug up, so is best avoided. Filtration should be efficient, but water movement fairly gentle. Frequent partial water changes will help keep nitrate to a minimum, particularly important as this species is sensitive to deteriorating water conditions. This fish, like other Gymnogeophagus species from colder climes, prefers the water to be a little cooler than most other South American cichlids (ideally 21-25 °C). Additionally, it is thought that a 3 month artificial winter is necessary for the longevity of Gymnogeophagus. To this end, the water temperature should be lowered to 16-18 °C for 3 consecutive months each year, so an aquarium chiller may be required to achieve this. Paraguay Eartheaters are best described as semi-aggressive and should be maintained singly, as a compatible pair, or one male with a harem of several females. Male fish will show much territorial hostility towards other males, particularly when ready to spawn. Tankmates should be chosen with care, avoiding small fish. Ideal companions should be of similar size and temperament, occupy the upper levels of the water column, and able to thrive under the same sub-tropical water temperature. May also be seen on sale as the Argentine Humphead.
Feeding
Omnivorous. Requires small aquarium foods compared to its adult size. Try to keep it varied with good quality carnivore and herbivore flakes, small sinking pellets, and a mixture of frozen foods such as white mosquito larvae, bloodworm, black mosquito larvae, vitamin-enriched brineshrimp, and daphnia.
Breeding
Delayed maternal mouthbrooder, which has been bred in the home aquarium. When ready to spawn, there will be a typical courtship display consisting of circling, fin-flashing, lateral displays, and mouth gaping. If the female is receptive, she will swim over the chosen pre-cleaned spawning site in a series of "˜dry runs"™, after which she will begin depositing eggs in small batches. The male immediately follows behind her and fertilises them, and this is repeated until the female is spent of eggs. The male is then driven away from the spawning site, and the female stays with the eggs, fanning them with her pectoral fins. If there are other females in the tank, the male may also spawn with them. The eggs will begin to hatch some 3-4 days later (the female will actually assist with this) and the wrigglers are taken up into her mouth where they are incubated for a further 14 days or so until they are free-swimming. At this point they can be offered Artemia nauplii and powdered flake food. If the female senses danger, the fry are urged back into her mouth as quickly as possible. Maternal care continues for several weeks.
