Matt Clarke on the Saddle cichlid, Aequidens tetramerus, a brightly coloured species that's recently appeared on the Czech Republic availability lists.
Common name: Saddle cichlid
Scientific name: Aequidens tetramerus (Heckel, 1840)
Origin: One of the most widespread South American cichlids. It is found in the Amazon, Tocatins and Orinoco basins and has been recorded in Peru, Colombia, Ecuador, Bolivia, Suriname, Guyana, French Guiana, Venezuela and Brazil.
Size: Museum data says up to 25cm/10", but most aquarium literature says it tops out at 15cm/6".
Diet: An omnivore. Stomach analyses of wild fish have revealed a diet of insects, vegetable matter and small fish. Aquarium fish take pellets, flakes and most frozen foods readily.
Water: Widespread and found in various types of water, so probably very adaptable. According to Kullander and Nijssen (1989) the pH ranges from 4.5 to 7.5, GH 1-13.5, temperature 24-26C/75-79F.
Aquarium: I kept a small group of subadult tetramerus a few years ago and found them quite aggressive and territorial with each other. I'd recommend getting a small group of young fish and growing them on together in a fairly spacious tank (120 x 60cm/4' x 2' would be good) and letting them pair off naturally. They're said to lay about 1000 eggs on submerged objects, such as rocks or wood. You'll need to provide quite a bit of decor for shelter, as dominant fish can be quite nasty to submissive specimens. While juvenile they should mix OK with most South American cichlids of comparable size, but I'd probably opt to keep them with cichlids larger than themselves (or alone) when adult and courting.
Notes: Aequidens tetramerus is the type species for the Aequidens genus. Although originally described by Heckel in 1840 as Acara tetramerus, it's subsequently redescribed by Dr Sven Kullander in 1996 using specimens from the west of Amazonia, and before that by Kullander in 1995 from fish collected in the Aripuana drainage, and Kullander and Nijssen in 1989 from Surinamese fish. Since it's so widespread, it's a common species in the wild, but it's rarely imported into the aquarium hobby. It's said to be most abundant in the floating rafts of aquatic vegetation that form in floodplain rivers.
Identification: Aequidens are tricky to identify because there is no recent key to the group and at least half a dozen undescribed species are known, for which there is currently no reliable identification data. The Aqualog Southamerican Cichlids III guide suggests that the species shows some variability in colour across the range.
Availability: Surprisingly, these specimens were actually captive bred fish from the Czech Republic, so they should be easy to obtain for most of the larger specialists who import their own fish. We spotted these on sale at Hobby Fish in Buckinghamshire (01908 543210).
Price: Very reasonable at just 5.99 each.
This article was first published in the March 2006 issue of Practical Fishkeeping magazine.