Fossorochromis rostratus was first described in 1899 by Boulenger, then under the name Tilapia rostrata. The genus Fossorochromis was founded in 1989 by Eccles and Trewavas.
The genus name Fossorochromis can be divided into two parts. “Fossor” means “digger” and is a reference to the way this species feeds. With their heads tilted downwards, they dive into the sand. They sift the sand through their gills in search of food. The second part is “chromis”, which is a reference to perch-like fish such as cichlids. The species name “rostratus” means “beaked”, a reference to the long and pointed snout that is somewhat convex in shape at the top.
Synonyms: Tilapia rostrata, Cyrtocara rostrata, Haplochromis rostratus, Haplochromis macrorhynchus.
In nature, Fossorochromis rostratus reach a maximum length of about 25 cm. In the aquarium, male specimens grow to about 35 cm; the females remain about 10 cm smaller.
Fairly elongated body that is moderately flattened laterally. The shape of the head, with a slightly convex profile, is well adapted to their diving behavior in the sand.
Color and markings
Juveniles and females have a silver-beige ground color and a pattern of black spots arranged in three longitudinal rows of five to six spots. Suppressed males also show this pattern, albeit on a silver-green ground colour. Dominant males get a beautiful plumage that is difficult to describe in words in terms of color shades and intensity.
Quite easy to determine in adult Fossorochromis rostratus (see “Colour and markings”). Even non-dominant males can be easily distinguished from the beige females by their grey-green ground colour.
Endemic species to Lake Malawi, distributed throughout the lake and quite common. Adults are usually found in groups (up to more than 50 individuals) above the sandy coast biotope. One of the indigenous names for this species is “Chigumbuli”, which means “smart person”. They owe this name to their skill in avoiding the trawl nets by diving into the sand.
Fossorochromis rostratus is one of the largest cichlids in the lake that survives by chewing through the sand. Observations in nature revealed that Fossorochromis rostratus lives in a commensal relationship with Cyrtocara moorii and Protomelas annectens. This relationship benefits the latter two, who benefit from it, as opposed to a symbiotic relationship, which benefits all parties. When looking for food, Fossorochromis rostratus dives headfirst into the sand, resulting in a swirling cloud of material from which Cyrtocara moorii and Protomelas annectens select the edible remains. Furthermore, Fossorochromis rostratus mainly feeds on plankton from the open water.
A sufficiently large aquarium with a sandy bottom and a few large stones on the bottom will suffice. We can also add plants without fear of them being eaten.
Breeding Fossorochromis rostratus
For breeding Fossorochromis rostratus we recommend a group consisting of one male and three to six females. It is in fact a polygamous maternal mouthbrooder, one male mates with several females who incubate the eggs in their mouths.
Breeding with this species requires some patience. They are only sexually mature from about 15 to 20 centimeters in length. Once a female is ready to mate, the male chooses a suitable place. This can be on top of a flat rock or he makes a small dent in the sand.
He lures the female by showing his best colors. He spreads his fins wide and shows his flank with trembling movements. When the female follows him to the spawning ground, spawning begins.
The fish circle around each other. The female lays a few eggs in the sand, turns and picks up the eggs in her mouth. The man continues to circle with her. Its anal fin shows a few egg spots. The female tries to pick up these egg spots, believing them to be eggs. The man then releases some sperm and fertilizes the eggs.
The nest can consist of up to 130 eggs. The female incubates the eggs for about 3 weeks. The number of young fish is so large that they can be seen in the throat pouch of the female.
The eggs hatch after a few days, but the young fish remain in the female’s mouth for a total of about three weeks. They then live on their egg yolk sac. After three weeks, the woman releases the fry. In case of danger, she takes (part of) the fry back into her mouth for a while.
In the aquarium, the young fish are quickly eaten. With luck, a few will survive among the rocks. If you want to keep more young Fossorochromis rostratus, you can catch the female around day 18 and place it in a separate aquarium. An experienced female holds the fry or picks them up later if she accidentally released some of them. Once the female has released the fry, you can place her back in her own tank.
The newly hatched Fossorochromis rostratus are large enough to eat freshly hatched brine shrimp nauplii and crushed flakes.
Walter Deproost, John de Lange
Proc. Zool. Soc. London (9) : 131-132.