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No federal permit to keepBig-mouth Hap
Tyrannochromis macrostoma
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Tyrannochromis macrostoma, or big-mouth hap, is a species of cichlid endemic to Lake Malawi where it prefers rocky shallows.
Care at a glance
Species-specific aquarium care
- Tank: At least 48 in long and 24 in front to back for one adult (adults commonly reach about 11.8 in / 30 cm).
- Water: Freshwater.
- Temperature: 73–81°F (range recorded for this species).
- pH: 7.4–8.4.
- Hardness: 7–30 dGH.
- Layout: Lives on or near the bottom: floor space and hiding places matter more than height.
- Diet: A predator: feed meaty foods sized to its mouth (frozen fish, shrimp, worms); it will eat tankmates that fit in its mouth. FishBase classes it as a carnivore.
Calculated from this species' own FishBase record: tank size from its typical adult length and swimming zone, water values from its recorded ranges. The group guide below fills in general care.
Care guide
Species care notes
- Tank: a base of at least 71 × 18 in (roughly 128 US gallons); space needed is rated “very large tank”.
- Water: hard, alkaline water, 75–82 °F, pH 7.6–8.8, 10–25 dGH.
- Behaviour: temperament predatory.
- Difficulty: Moderate (Seriously Fish rating).
Short excerpts from the species profile:
- Setup: “The tank can be quite sparsely decorated but provide some large rocks to act as cover.”
- Diet: “Will accept dried foods such as pellets but these should not form the basis of the diet.”
- Tankmates: “A predatory species with a large mouth that should not be kept with fish under around 5" in length as they will be eaten.”
- Breeding: “Not known to have spawned in aquaria.”
From the Seriously Fish profile for this species, which has the full habitat, maintenance, diet, behaviour and breeding write-up 167
Lake Malawi peacocks and haps
Applies to most species in this group. Habitat: Open water and sand of Lake Malawi. Individual species can differ, so compare with the species numbers above and the linked sources.
Housing & setup
- Hard, alkaline water (pH 7.8–8.6), a long tank (5 ft+ for larger haps) with open sand and some rock.
- Generally less aggressive than mbuna; males color up best with several females.
Climate & lighting
| Water | 76–82°F |
Diet
- For Aulonocara stuartgranti, use small prepared foods with some vegetable content and varied small live/frozen invertebrates. Match other haps to their own feeding ecology.
Health watch
- Do not diagnose bloat from a label such as “mbuna-style food”; Aulonocara stuartgranti diets can include vegetable foods. Match food and tankmates to the species.
Understanding the animal
About this animal
About this animal
This species can reach a length of 30 centimetres (12 in) TL. It can also be found in the aquarium trade.
Quoted from the Wikipedia article “Tyrannochromis macrostoma” (CC BY-SA 4.0) 174
In the wild
In the wild
From this species’ own FishBase record (habitat, bottom type, water and breeding data), not its family. Good care copies these conditions.1
| Where it lives | Lives in freshwater, in lakes. Stays near the bottom. Found over rocky areas in shallow water. |
| Water it lives in | Freshwater, 73–81 °F (23–27 °C), pH 7.4–8.4, hardness 7–30 dH. |
| Climate | Tropical climate. |
| Wild diet | Hunting macrofauna (predator). |
| Behavior to plan for | Breeding: clutch tenders. |
What this means for care
- Keep water within its wild range, 73–81 °F.
Native climate (measured)
Native climate (measured)
| Warm-season highs | about 87°F (up to 90°F in the hottest sampled areas) |
| Cool-season lows | about 60°F (down to 56°F in the coldest sampled areas) |
| Average temperature | 71–76°F across sampled records |
| Relative humidity | 67–70% on average (driest month about 55%) |
| Rainfall | about 1230 mm a year, with strong wet and dry seasons |
Measured at 22 wild occurrence records sampled against WorldClim 2.1 climate data (1970–2000 averages). Air conditions in the range are ecological context, not enclosure settings: microhabitats such as burrows, leaf litter or basking rocks can be cooler, warmer or more humid.
From the sources
From the sources
Quoted from the matching sections of reputable sources for this exact species. Specialist databases are used first; Wikipedia (community-edited, CC BY-SA 4.0) only fills gaps. Other sources are short credited quotes.
| Where it lives | Home ranges Population dynamics Growth parameters Max. ages / sizes Length-weight rel. Length-frequencies Mass conversion Recruitment Abundance Life cycle Reproduction Maturity Maturity/Gills rel. — FishBase |
| Reproduction | Guards offspring for more than 3 weeks. Young become independent when they reach 3.8-4.0 cm SL and are able to move around as solitary hunters in the rocky habitats. — FishBase |
| Biology | Found over rocky areas in shallow water. Piscivore, feeds by moving around rocks and into cracks in search of its unwary prey, the Mbunas, which are quickly snapped up with the large mouth. — FishBase |
Data and studies
The numbers
The numbers
Each bar is what one source reports. Where several sources weigh in, the dashed gold band marks their average.
Adult length
Maximum recorded length. Measured as total length. Fish in home aquariums often stay smaller than wild records.
Water temperature
Range the species tolerates in nature; aim for the middle.
Water hardness
Minimum tank footprint
Seriously Fish recommends a tank base of at least 71 × 18 in (about 128 US gallons).
Sources for this sheet
- FishBase (Froese & Pauly, eds.), version 24.07 Peer-reviewed researchThe global scientific database on fishes, maintained by a consortium of research institutions; every value is referenced.
- Seriously Fish species profiles Experienced keeper or breederLong-running aquarium reference written and peer-checked by experienced fishkeepers and ichthyologists; each profile covers habitat, tank size, water, diet, behaviour and breeding.
- Merck Veterinary Manual: Management of aquarium fish Zoo, university or veterinaryThe Merck Veterinary Manual: a standard veterinary reference written and reviewed by veterinary specialists.
- Merck Veterinary Manual: Types and features of aquatic systems Zoo, university or veterinaryThe Merck Veterinary Manual: a standard veterinary reference written and reviewed by veterinary specialists.
- Merck Veterinary Manual: Nutritional diseases of fish Zoo, university or veterinaryThe Merck Veterinary Manual: a standard veterinary reference written and reviewed by veterinary specialists.
- Seriously Fish — Aulonocara stuartgranti Zoo, university or veterinaryAdded in the 2026 source-checked care-guide review.
- Wikipedia (species article) Community referenceFree encyclopedia; useful overviews with their own citations. Intro text is quoted under CC BY-SA 4.0.
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