Petrochromis Trewavasae care guide
Petrochromis Trewavasae (Petrochromis trewavasae) — minimum tank 600 L, temperature 24-27 °C, pH 8.5-9.2.
Compiled by Aquairi from published sources · Published · Updated
Overview
Petrochromis trewavasae is a large Tanganyikan herbivorous cichlid reaching about 20 cm, named in honour of ichthyologist Ethelwynn Trewavas. The species inhabits the wave-zone rocks along the Burundian and Tanzanian shores; adults bear a slate-grey body with subtle bluish iridescence.
Taxonomy
- Family: Cichlidae
- Genus: Petrochromis
- Scientific name: Petrochromis trewavasae
- Common synonyms: Goldfin Petro
Habitat
Endemic to Lake Tanganyika, where it grazes the algal turf on rocky shores. Tanganyika water is hard and alkaline (pH 8.5-9.2, KH 12-20), with stable warm temperatures and very high dissolved oxygen. Petrochromis species are confined to specific stretches of shoreline and form large foraging groups over the upper rocky zone.
Tank requirements
- Minimum tank volume: 600 L (158.5 US gal)
- Adult size: 17-20 cm
- Temperature: 24-27 °C (75-81 °F)
- pH: 8.5-9.2
- GH: 12-25 °dGH
- Water flow: medium
- Lifespan: 10-15 years
- School size: ≥6 individuals
Diet
A strict aufwuchs grazer with tightly packed comb-like teeth used to scrape biofilm from the rocks. In aquaria a vegetable-rich diet of spirulina pellets and blanched vegetables is essential; protein-heavy diets cause severe bloat. Large adults consume substantial quantities of food.
Compatibility
Aggressive and territorial; demands very large tanks (500+ L) with extensive rockwork and a single-species colony or pairing with other large herbivorous Tanganyikans. Do not mix with smaller mbuna-style fish that cannot withstand the pressure; multiple males must each have enough rock territory.
Breeding
A polygamous maternal mouthbrooder. The male defends a small flat rock and entices females to spawn; the female holds eggs and wrigglers for about four weeks before releasing the fry, which already feed on aufwuchs.
Conservation status
IUCN Red List: see species page. Most Petrochromis are widely distributed within Lake Tanganyika and assessed as Least Concern; however, the genus is collected for the ornamental trade and shoreline-specific morphs are more vulnerable.
Breeding Petrochromis trewavasae
Overview
Petrochromis trewavasae is a large algae-grazing cichlid endemic to Lake Tanganyika, where it lives on shallow rocky substrates and feeds by scraping the biocover (aufwuchs) from rocks. FishBase records a maximum length of about 18 cm and confirms that females brood their young in the mouth, making this a maternal mouthbrooder. Within the genus Petrochromis, breeding follows a consistent pattern, so closely related species such as P. famula provide a reliable model for captive reproduction.
Sexing
Sexual dimorphism in Petrochromis is subtle. As documented for the genus on Seriously Fish, mature males tend to be more colourful and develop pointed dorsal, anal and pelvic fins, while females remain plainer. Reliable visual sexing usually requires adult, well-conditioned fish, and many breeders rely on observing spawning roles to confirm sex.
Conditioning
Petrochromis are specialised rock-grazers and must be fed a diet high in fibre and low in protein. Excess protein is associated with digestive disorders in this group, so conditioning should centre on vegetable-based foods such as spirulina flake and blanched greens, with only sparing use of richer items. Maintaining a colony in spacious, well-filtered, well-oxygenated water supports the steady condition needed for spawning.
Breeding Setup
Because of their adult size and aggression, these fish require very large tanks with a rocky aquascape providing open grazing surfaces and broken sightlines. A single male with several females is the typical breeding configuration; intraspecific aggression is intense and is best diffused by keeping the colony with robust tankmates rather than alone. Hard, alkaline water within the temperature range of 24-27 °C suits the species.
Spawning Behavior & Trigger
Spawning follows the maternal mouthbrooding pattern typical of the genus: the female takes the eggs into her mouth, where they are fertilised, and then carries the developing brood. Good water quality and steady conditioning on the correct herbivorous diet are the main triggers. The dominant male defends a grazing territory and courts receptive females within it.
Egg & Fry Care
Based on the closely related P. famula, the female carries the brood for around four weeks and does not feed during this period. Released fry of Petrochromis are large and accept adult-sized foods almost immediately, growing quickly when fed frequently. As with conditioning, fry and adults should be kept on a fibre-rich, low-protein diet to avoid digestive problems.
Common Challenges
The two principal challenges are aggression and diet-related disease. Intraspecific aggression can be severe in species-only setups, so adequate volume and tankmate diversity are essential. Feeding too much protein risks the digestive bloat that the genus is prone to. Sexing difficulty and the slow maturation of these long-lived fish also make breeding an advanced undertaking.