Matt Clarke looks at the Soda cichlid, Alcolapia (formerly Oreochromis) alcalicus, an extremophile from Lake Natron.
Common name: Soda cichlid
Scientific name: Alcolapia alcalicus
Size: Males can reach 8cm/3" SL.
Origin: Endemic to Lake Natron, a 56 x 22km soda lake in the African Rift Valley east of Lake Victoria. Lives around the shoreline hot springs and creeks.
Water: An extremophile. This fish has evolved to live in hot, sodium-rich water with a pH of 9.5-10.5 (that's about 100 times more alkaline than Malawi) and a KH of 7280! The sg is 1.2 and the temperature is typically around 30-32°C, but sometimes much higher. Thankfully, it also fairs well in much less alkaline tapwater (pH 8ish) but does best at a high temperature of, say, 28°C+.
Diet: Gut analyses of wild fish show that 90% of the diet consists of blue-green algae, supplemented by copepods and insect larvae. Mine feed ravenously on flakes.
Habitat:This fish lives among thick trona (sodium and carbonate) deposits in waters that are stained pinky-red from the abundant bacteria and Myxophyceae present, usually around the swampy margins near hot springs.
Aquarium: These small tilapiines are ideal for the smaller aquarium. They're relatively placid and appear quite simple to keep and develop stunning colours. My two males and three females are doing well in a 90cm/36" tank furnished with rocks and sand.
Sexing: Males are much more colourful.
Breeding: A maternal mouthbrooder which breeds throughout the year. Males build small pits to spawn in but leave them in the early morning to graze on algae. After the 12-16 mouthbrooding period, there is no parental care. The sister species A. grahami has spawned at sizes as small as 2.5cm, which may be a record for a tilapiine cichlid.
Similar species: There is one other species in the Alcolapia genus, O. grahami. Both fish were previously considered subspecies of Oreochromis alcalicus and were placed in Dr Ethelwynn Trewavas's Alcolapia genus. They are now considered distinct species and the status of the subgenus has been raised. Both are rare in the trade. There's also another cichlid found in nearby Lakes Manyara and Kitangiri, the very rare Oreochromis (Vallicola) amphimelas, which Trewavas believed to be a close relative. According to Lamboj, some other species are also recognised in the genus.
Identification: Males alcalicus have a yellow throat and belly (white in grahami) and a red posterior portion to the caudal fin (orange in grahami). O. grahami also has a black bar through the eye at certain times. The ecology of the two species is slightly different, too. A. grahami tends to feed most in the evening while A. alcalicus feeds in the morning.
Notes: Physiologically, this is an oddity. Unlike most other fish, this species is ureotelic - it produces urea instead of ammonia as its waste products. It also has a specially adapted gas bladder to allow it to utilise surface oxygen and often gulps at the water surface.
Availability: These fish haven't been available in the trade before. They were imported from the Czech Republic by Tom Halvorsen Ltd.
Price: A seriously fascinating cichlid. Prices range from £20-40 each.