Altolamprologus calvus

The calvus is instantly recognized by its body, which looks large from the side but almost knife-thin from the front. This compressed shape lets it slip into rock crevices and hunt the eggs, fry and small invertebrates hiding there. It carries small white spots on a dark brown–black or light gray background; its pointed, upturned mouth is typical. Thick, tough scales protect it from the bites of other fish.

It grows very slowly; it takes several years for the small specimens sold to reach adult size. It is a calm, slow-moving and curious fish; with the right companions it is a favorite of Tanganyika aquariums.

• Black: white spots on a dark brown–black background; the best-known form.
• White: spots on a light gray–beige background.
• Apart from these, local forms named after their collection site, such as "Inkisi" and "Chaitika", are also sold; the forms should not be mixed with each other.

It lives along the rocky shores of the southern part of the lake, among rock piles and crevices. It glides close to the rock surface alone or in loose pairs, probing the crevices one by one. Each area where it occurs has its own distinctive color form.

• Volume: 150 liters for a pair; 200 liters or more with other Tanganyika species.
• Rockwork: plenty of narrow crevices and caves; crevices suit both its hiding and its hunting habits.
• Shells: a few large snail shells, or narrow crevices only the female can fit into, are essential for the female to spawn.
• Water: pH 8–9, hard and stable; a 25% water change every week.
• Substrate: fine sand.

Carnivorous. Frozen mysis, brine shrimp, cyclops and krill along with a quality carnivore granule are suitable. Because it eats slowly and cautiously, make sure food reaches it too when it is kept with fast fish. Do not give live feeder fish.

Peaceful toward fish too big to fit in its mouth; those that do fit, it patiently stalks and hunts. Fry of other species, shell-dwelling cichlids and small fish are at risk.

Good companions: large Julidochromis species (regani, marlieri), adult Cyprichromis, Synodontis catfish; frontosa in a large aquarium if the calvus is adult-sized.

Avoid: shell-dwelling cichlids and all small fish, shrimp, aggressive Malawi mbuna.

• Kept as a pair or as 1 male : 1–2 females.
• The easiest way to form a pair is to grow up 5–6 juveniles together; since they grow slowly, this takes time.
• The male becomes noticeably larger than the female. This difference is the key to breeding: the female spawns in a narrow crevice or shell the male cannot enter.
• More than one male can live together only in a large aquarium with plenty of rockwork.

The female chooses a narrow crevice or a large snail shell that she can fit into but the large male cannot enter. The eggs are laid there; the male fertilizes them at the entrance and defends the territory outside, while the female tends the eggs and fry. The fry become free-swimming after about a week to ten days and are fed newly hatched brine shrimp. The fry also grow slowly.

• Hardy; problems usually come from soft water, low pH and high nitrate.
• Bloat: can occur as a result of overfeeding and a monotonous diet.
• Because it eats slowly, it can go hungry next to dominant fish; watch for signs of weight loss.

Adult males are noticeably larger than females (male around 13–15 cm, female around 10 cm) and have a higher back. It is difficult to tell juveniles apart; the size difference only becomes clear after a few years.