There are several morphological varieties of Alto. calvus: black, white, yellow, and even zebra, which looks a lot like a white version of Alto. compressiceps. The black calvus is found at several different locations in Lake Tanganyika, although the populations from Zambia and Moliro have been more heavily exploited for the cichlid hobby. The one shown here is a wild-caught male from Moliro. The white variety (pictured below) is found exclusively at Chaitika.
Before I say anything more about this fish, I should note that this first photograph is not a fair representation of a black calvus. A black calvus really belongs over a dark substrate, and this photo was snapped while the fish was over a white substratum. When kept over a dark sand, it will turn very dark and its white spots will sparkle and glow. The stripes of the White Calvus are less apparent when kept over a light substrate, but stripes and spots become more apparent when kept over a dark substratum. The white calvus differs markedly from the black variety in that its spots extend all along the ventral fins.
Alto. calvus is characterized by a laterally compressed body, a steep sloping forehead, stripes that are more apparent on the head and collar region, and brilliant white spots that decorate the posterior two-thirds of their flanks. Adult males can attain maximum lengths of six inches, while females max out at around four inches. Once mature, males are also higher-bodied and possess more elongated fins.
Alto. calvus is a predator, and specializes in snatching young cichlids and invertebrates from between rock crevices and rock piles. Their laterally compressed body not only helps them in avoiding detection, but permits them to go into narrow crevices, turning their bodies at odd angles if needed. Small fishes, such as juveniles and shell-dwellers, should not be kept in the same tank with this fish as the calvus may dine on them.
When hunting, Alto. calvus will cruise along the substrate looking for prey. Once a target has been identified, this fish will keep its eye locked on the prey, but raises its body upwards and then strikes. This hunting technique is similar to Dimidiochromis compressiceps, which is another laterally compressed predator.
In the aquarium, they can be given any type of live or frozen food (except beef heart or any other food containing mammalian products). Live food is always greedily consumed. Flake food is accepted, but is usually insufficient alone to bring a female into breeding condition.
Calvus make a great addition to most any Tanganyikan community setup, barring a setup with shell dwellers. They can also be kept with many of the fishes from Lakes Malawi and Victoria, provided the latter also require a high protein diet. Mbuna are not ideal tankmates for this reason.
They make a great addition to many setups because they tend to mind their own business, but can certainly hold their own. The thick scales of "Altolamps" give them an efficient protection against attacks by fry-guarding cichlids. I have read that when attacked, they will bend their bodies so as to expose their scales to an enemy, which will easily fray the lips of an enemy when bitten.
Calvus looks particularly menacing, but is rather mild. They are not territorial and not aggressive towards other cichlids of similar size. In fact, this male will often poke his head into part of the holey rock in my tank, pretending that no one can see him because he can't see them! When introducing an "Altolamp" to your aquarium, don't be alarmed if it hides for several weeks before it becomes comfortable with its surroundings. Just be patient and ensure good water quality. Don't overfeed in your anxiety that it eat; this will only degrade water conditions and cause other cichlids in the tank to become more susceptible to Bloat.
Altolamprologus species are substrate spawners. It is not uncommon to miss this fish spawning, as it is a very secretive spawner. Spawning takes place in a cave, shell, or flowerpot too small for the male to enter. The male will release his milt at the entrance. Both the male and female will then fan their fins to direct it to the eggs, which have been dropped on the substrate. Typical spawns may number as many as 200. Females can spawn every 25-35 days when kept in condition. The eggs take more than a week before they hatch and are mature enough to move out on their own. The fry are quite large, but require a very long time to grow to maturity. For example, it may take six months or more for an "Altolamp" to reach 1.5 inches.
All Altolamprologus species operate alone, although several Altolamprologus can be kept in the same tank. Personally, I have not kept more than one variety of "Altolamp" in any one tank, although there are some out there who purport that different species and color morphs of Altolamprologus can be kept and bred in the same aquarium. Notwithstanding, there are probably just as many, if not more, who would discourage it. They are best kept and bred as pairs, but can also be kept as a colony.