Cichlids are a diverse family of teleost fish that live in Africa, America, Asia and Madagascar. They are well known among aquarium enthusiasts for their intense coloration, a wide range of reproductive modes, but also for their aggression against tank mates. Apart from discus and angelfish, African cichlids from lakes Malawi, Tanganyika and Victoria dominate the aquarium trade. They are colourful, easy to breed and some species don’t even require very large aquariums. Central American cichlid species are favoured by owners of large “monster fish tanks” because they tend to get quite large, while being colourful as well. Contrary to that, South-American dwarf cichlids of the genus Apistogramma are enjoyed by owners of smaller aquariums. However, there is yet another group of cichlids from South America that is overlooked a lot, although they bring most assets fish keepers are looking for. They are colourful, majestic-looking, they behave well with other fish and some members of the genus even tolerate cool water temperatures around 15 °C! These are of course earth-eaters.
Earth eaters – fish that eat sand
The name earth eaters is used for genera Acarichthys, Geophagus, Gymnogeophagus and Satanoperca. These schooling fish sift through the sandy bottom of the waterbody they inhabit to search for small aquatic invertebrates. They do so by “eating” sand, apparently chewing it and spitting it out while keeping their prey items within their oral cavity. Typically, most earth eaters grow to about 15-25 cm, which makes them suitable for aquariums of 350 l and bigger. Of course, this is not a tank size for everyone, but keepers get rewarded with fascinating behaviour. For most species it is recommended to keep pairs or small schools of 6 or more specimens. There are different modes how earth eaters reproduce. Some species will lay eggs on open spaces like on rocks and will guard their fry. Others will spawn on substrate, but as their larvae hatch, they will switch to mouth-breeding.
What do earth eaters eat?
As they are dominantly carnivorous bottom-feeders, their diet should be of the sinking type. Earth eaters will gladly accept live food, frozen/thawed food and commercially produced granules, flakes or chips such as Krill Gran, Soft Line America Size M, Tropical D-Allio Plus Granulat, Tropical Cichlid Gran and Tropical Discus Gran D-50 Plus. Generally, earth-eaters are not picky. Quite the opposite, they are hungry all the time. Because of their appetite, regular water changes are necessary to keep nitrate levels low and the animals healthy.
Regarding other water parameters, there are some differences among the various earth-eating species. Satanoperca and Acarichthys species are typical Amazonian lowland (blackwater) inhabitants of streams and rivers that require warm (26 – 30 °C) water with low pH value (5,0 to 6,5) and low carbonate hardness (<10). Gymnogephagus species occur as far south as Uruguay, which means they are tolerant to temperatures way below 20 °C and they are not as demanding in terms of water parameters. Gymnogeophagus terrapurpura males are impressive cichlids of medium size that develop rather massive nuchal humps and intense blue, red and greenish body colouration. It seems like they require a cool phase to induce reproductive activities.
Most earth-eaters are suited for typical Amazon community tanks with fine substrate, some driftwood and dim lighting, because they are not active fish predators. They live well with most catfish species and medium-sized tetras like the Buenos Aires Tetra (Hyphessobrycon anisitsi). Due to their digging activities, fine plants in a tank are not the best option. The fish do not actively eat most plants though, so you can still have some large Cryptocoryne, Anubias or Java Fern in a Geophagus tank.
Species of earth eaters
The most common earth eater in the fish hobby is probably Geophagus brasiliensis, a relatively large, hardy, but calm species that occurs in south-eastern Brazil. Because of their unique morphology and ecology, their genus name is often written in quotation marks to express their possibly different phylogeny. Aquarium populations have often been collected at various localities, which can be seen in their looks.
Probably the smallest Geophagus is the currently undescribed Geophagus sp. “Gurupi”. These fish are not hard to breed, however they are not commonly available.
One of the most colourful, readily available earth-eating species is Geophagus sp. “Tapajos” commonly known as “red head”. Males of this species develop a certain nuchal hump that is bright red or orange. They are facultative mouth-breeders that show a certain level of inter- and intraspecific aggression despite their relatively small size (under 20 cm for adult fish). Therefore they should be keep in relatively large aquariums.
If all of this sounds interesting to you and if you don’t like the stone optics of most Malawi-tanks, earth eaters might be a good option for you – especially when your aquarium is large enough to host a whole school so you can observe their interesting behaviour!