Demon eartheater

Satanoperca jurupari is an Amazonian eartheater, found over sand and mud in slow stretches of river and floodplain lake from Peru and Ecuador across to Brazil and Bolivia. The 'demon' in its name is a Tupi forest spirit, not a comment on its manners — in the tank it is one of the calmer large cichlids and will not bother anything it cannot fit in its mouth. It grows to about 18.5 cm.

The detail that decides whether this fish thrives is the substrate. It feeds by taking mouthfuls of sand, sifting out insect larvae, small crustaceans, seeds and detritus, and passing the grit back out through its gills. Coarse gravel blocks that behaviour and can wear down the gill rakers, so a deep bed of soft sand is essential. Beyond that it wants dim light, some driftwood and open floor space.

Keep it as a group of five to eight; in ones and twos, weaker fish get bullied and the group stays nervy. A footprint of roughly 756 litres suits a group. These cichlids are unusually sensitive to nitrate and prone to head-and-lateral-line erosion, so this is a fish for a mature tank with 50–70% weekly water changes, held at 20–28 °C and pH 5.5–7.5.

Feed several small portions a day rather than one big meal — fine sinking foods, frozen bloodworm and brine shrimp, plus something with vegetable content. It is a delayed maternal mouthbrooder: the female collects the fertilised eggs and carries the brood in her mouth until the fry are free swimming.