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Tyrannochromis macrostoma

Big-Mouth Hap

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Last revised 2026Edit this page

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Tyrannochromis macrostoma adult male
Tyrannochromis macrostoma adult maleJJPhoto

Quick factsEdit

Max size
350mm SL14in SL
Aquarium size
180 × 45cm72 × 18in
Temp
24–28°C75–82°F
pH
7.6–8.8
Hardness
10–25dGH

Difficulty5 of 8 measures

Moderate

How the rating is worked out

Space
very large tank
Water
flexible
Temp
needs a steady temperature
Diet
unknown
Temperament
eats smaller fish
Social
one male with several females
Compatibility
unknown

Other demands

Each of these can raise the rating on its own, whatever the measures above say.

Hardiness
unknown
  • Needs a very large tank

The big-mouth hap, Tyrannochromis macrostoma, is a large predatory cichlid endemic to Lake Malawi, living in shallow rocky areas. An ambush predator, it often attacks prey while swimming upside-down, and its reverse countershading (a belly darker than its back) is thought to make it harder to spot. Mbuna are its natural diet, and juveniles are easily confused with T. nigriventer.

Distribution

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It inhabits shallow waters in rocky areas.

Aquarium size

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Standard length
350mm SL14in SL
Aquarium base
180 × 45cm72 × 18in
Volume
~486litres~128US gal

180 ∗ 45 ∗ 60 cm72 ∗ 18 ∗ 24 in - ~486 litres~128 US gal.

Maintenance

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The tank can be quite sparsely decorated but provide some large rocks to act as cover. A substrate of sand is the best option. Obviously, powerful filtration is required in order to deal with the large amounts of waste produced by this predatory fish.

Water conditions

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Temperature
24–28°C75–82°F
pH
7.6–8.8
Hardness
10–25dGH

Temperature: 24 – 28 °C75 – 82 °F

pH: 7.6-8.8

Hardness: 10-25°H

These recommendations come from this profile’s own figures. They contain affiliate links, so we may earn a commission.

Will accept dried foods such as pellets but these should not form the basis of the diet. Although this fish is a piscivore by nature, it can easily be trained to accept dead foods in aquaria. Prawns, mussel, cockle, lancefish etc. are all ideal.

Behaviour and compatibility

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A predatory species with a large mouth that should not be kept with fish under around 5" in length as they will be eaten. This is particularly true for mbuna, the natural diet of this fish. It is peaceful with species too large to eat, and can be combined with other large haps, but do not keep it with species requiring a vegetarian diet.

The male fish become territorial during spawning. Several females should be kept per male, and only one male kept, unless the tank is enormous.

Sexual dimorphism

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Adult males are more colourful than females.

Reproduction

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Not known to have spawned in aquaria. Maternal mouthbrooder. In nature males excavate large, crater-like pits in the substrate and defend these against other males. Spawning occurs in these pits. Brood care by the female is known to last for some time in this species.

Notes

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T. macrostoma is an ambush predator in nature, lurking behind rocks and in crevices as it stalks its prey. It is rarely seen in the hobby and is usually quite expensive. Juveniles are easily confused with the similar T. nigriventer, but are easily distinguished when adult, as nigriventer does not develop the dark belly of macrostoma.

Interestingly, this species exhibits reverse countershading, as also seen in the common Upside-down catfish, Synodontis nigriventris. This means that unlike the majority of fish species, it's belly is darker than it's back. In T. macrostoma, this is thought to derive from the fishes' hunting technique, as it often attacks prey whilst swimming upside-down, the reverse countershading making the fish harder to spot.

Distribution

Profile completeness20 of 24

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