Megasema Eartheater (Geophagus megasema)

Geographic Origin and Biotope: Endemic species of the Guaporé River basin (Bolivia and Brazil). Lives in rivers with moderate currents and boundless bottoms of light sand or clay to sift.

Taxonomy and Morphology: Megasema Eartheater (Geophagus megasema). Robust but elegant South American cichlid. Belonging to the "surinamensis" group, it is distinguished by a gigantic ("mega") ocellar spot ("sema") on the flanks and an imposing muscular profile.

Social Behavior: Distinctly gregarious fish; keeping singles or pairs leads to chronic shyness. To mitigate inter-male aggression, they need to be kept in schools of at least 5-8 specimens. Dominants develop nuchal humps.

Coloration and Sexual Dimorphism: Coppery/sand background, with the unmistakable (very wide) black spot on the flank. The fins are a cascade of turquoise, red and golden lattices with very long filaments at the end of the tail in mature males.

Aquarium Setup: A 150 cm (60 inches) tank is needed. Only true absolute rule: the bottom must be a thick layer of pure sand (sugar-grade, or washed building sand). Do not insert medium quartz: they spit it out, but they flay their gills.

Diet and Feeding: Geophagous ("earth eater"). Takes shovelfuls of sand, swallowing them and sifting with the food through the gills. Provide a fast-sinking omnivorous cichlid pellet and rain down bloodworms and brine shrimp.

Water Quality: Despite their size, they are sensitive to an excessive load of nitrates. So as not to slow down their growth or develop the hole-in-the-head scourge (HITH), change at least 40% of water a week with excellent siphoning.

Compatibility and Tankmates: Formidable pairings with schools of large South American tetras (Penguin tetra, Buenos Aires tetra) which reassure the group by staying on the surface. Excellent with Loricariids, terrible and unsuitable with biting cichlids like Jack Dempsey or Midas.

Aquarium Reproduction: Larvophile mouthbrooders. The pairs lay on a clean flat stone, but as soon as the young hatch from the egg (2-3 days), both parents put them in their mouths in turns protecting them for over 2 weeks.

Risks and Diseases: Sharp gravel and nitrate accumulations cause the onset of the lethal Hexamita (Hole-in-the-head disease) on the head. Food competition with fast surface fish (e.g. sharks or large barbs) makes them lose weight dramatically.