Taxonomy & naming
Haplochromis sp. "Ruby Green" has no scientific name. It is one of the many haplochromines of the Lake Victoria region that hobbyists and researchers know only by a working label, and because the Catalog of Fishes lists only formally described species, the fish has no entry there. The Cichlid Room Companion traces the label to Erwin Schraml's 1994 account of new cichlids from Uganda in DCG-Informationen, the German Cichlid Association's journal.
The genus placement is provisional. Haplochromis is used here in the broad sense the hobby applies to Victorian and Kyoga haplochromines awaiting formal revision, not as a claim about where a description would eventually put it. The name itself is purely descriptive of the breeding male, and keepers write it with varying capitalisation and quotation marks; CARES lists it as Haplochromis sp. 'ruby green'.
Morphology
Aquarium specimens reach about 5 in, according to the Nordic Cichlid Society's species register; no measurements from wild-caught type material exist, because no type material exists.
The sexes differ clearly. Males are red over the back and on the fins and carry more numerous, sharper egg-spots on the anal fin. A few days before spawning, a male's breeding dress develops further, turning olive green below the dark diagonal stripe that runs across the flank. Females lack the red and carry fewer, fainter egg-spots.
Habitat
The species belongs to the Lake Kyoga system, the broad, shallow lake and swamp complex on the Victoria Nile downstream of Lake Victoria. The Nordic Cichlid Society register records two collection points: Lake Kyoga itself and Lake Nawampasa, one of the small satellite lakes in the swamps of the system's south-east. A Danish keeper who has collected in Uganda since 2014 reports a wider picture: he has found it across the Kyoga system, in small and large lakes, clear and turbid water, and even in the flowing Nile, persisting in places where other haplochromines have vanished.
Nawampasa is a shallow lake set in dense papyrus swamp. The Key Biodiversity Areas factsheet for the surrounding Lake Nakuwa site, which includes Nawampasa, describes the lake as very shallow and covered by water-lilies, with short sedges on the drier margins and the surrounding papyrus broken by pools and floating mats (sudd). That fits what keepers report of the fish's preferences there: it is found where aquatic plants grow thickly. No field water chemistry has been published for any of its habitats, so this page carries no hardness figure.
Feeding
At Lake Nawampasa, Ruby Green grazes on submerged plants. A keeper who maintains a Nawampasa line describes the fish scraping or nipping epiphytes — the film of algae and small organisms coating aquatic vegetation — from plant stems and leaves, and the Nordic Cichlid Society register likewise records it grazing algae from water plants. The same keeper cautions that populations elsewhere in the Kyoga system, living in very different lakes, may have other feeding habits; nobody has studied them.
The Nawampasa diet places it among the algal grazers, a feeding guild still present in the Kyoga satellite lakes but absent from the main lake's catches. Surveys of six satellite lakes in 1996–1998 found seven haplochromine feeding guilds, including algal eaters and higher-plant eaters, against only two in Lake Kyoga proper (Mbabazi et al. 2004).
Mating
Ruby Green is a relatively peaceful haplochromine for most of the year. Males become mildly territorial only around spawning, when they take on their fullest colours, including the olive-green breeding flush below the flank stripe. In aquaria they choose spawning sites beside stones or under roots with an overhang.
As in other Victorian haplochromines, the female takes the eggs into her mouth to brood them. Subordinate males are ready to step in: one Danish breeder, after removing his dominant male, found the same female spawning with the second-ranked male, and later with a third.
Breeding
The female is a maternal mouthbrooder. The Nordic Cichlid Society register gives a brooding period of about 15–18 days and broods of roughly 20–30 young; one Danish breeder reports about 21 days. Keepers describe the species as easy to breed once it is kept well.
Because every fish in the hobby descends from a small number of wild imports, breeders urge one another to exchange males between lines to keep captive stocks genetically healthy. Lines should stay separate from other Victorian and Kyoga haplochromines: the females of many species are grey-green and nearly impossible to tell apart, and haplochromines cross readily, so mixed stock loses its value as a record of a wild population.
In the aquarium
Sources disagree on how demanding Ruby Green is. The Nordic Cichlid Society rates it an advanced species and suggests a minimum of 35.5 in and 40 US gal, while a Danish breeder who has kept it for years reports no particular difficulties but recommends tanks from about 80 US gal. Both agree on 72–82 °F; the register gives a pH of about 7.5–8.
Give the fish plants and plenty of cover, since it is relatively shy, along with rockwork or roots with overhangs for spawning. It can be kept as a pair or in a larger group. Suitable companions are peaceful mbuna and other mild-mannered Victorian haplochromines; avoid keeping it with other haplochromines whose females it could cross with.
The register notes a high metabolism and a correspondingly large appetite, and suggests a shrimp-based mix with astaxanthin. The Danish breeder instead feeds a mostly plant-protein staple with a weekly fasting day — closer to the fish's grazing habit at Nawampasa.
Conservation
Ruby Green has a conservation history under another name. A Lake Nawampasa haplochromine listed as Haplochromis "ruby" — which the Nordic Cichlid Society register equates with this fish — was assessed Critically Endangered in the 1996 IUCN Red List of Threatened Animals. That entry no longer appears on the current Red List, and the Cichlid Room Companion records the fish as not evaluated, so it has no current IUCN assessment. CARES classifies it as Vulnerable, its category for species facing a high risk of extinction in the wild in the medium term (assessed 15 January 2017), and keeps it on its priority list for hobby breeding.
Its best-documented refuges are the Kyoga satellite lakes. After the introduced Nile perch collapsed the haplochromine fauna of Lakes Kyoga and Victoria, a survey found that the small satellite lakes still held 37 of the 41 haplochromine species it recorded, compared with only 14 in Lake Kyoga itself; the papyrus swamps separating them from the main lake had kept the predator out (Mbabazi et al. 2004). Mwanja et al. (2001) had already drawn attention to these minor lakes as refuges for fish lost elsewhere in the Lake Victoria region. Field reports of Ruby Green from the main lake and the Nile suggest it is hardier than many of its relatives, but no survey has measured its status anywhere.
The satellite-lake protection is only as strong as the swamps. The Key Biodiversity Areas assessment for the Lake Nakuwa site, which includes Nawampasa, lists smallholder farming, livestock grazing, more frequent fires, fishing, and plant gathering as ongoing threats, and the Cichlid Room Companion notes eutrophication and habitat loss as concerns for this species. Well-documented captive lines are an insurance policy while its wild status remains unknown.