Fossorochromis rostratus (Malawi Sand Diver) Care & Species Profile

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This dazzling large Hap is one of the well-known Lake Malawi Cichlids in the hobby due to its bright colors and moderately aggressive nature.

However, Fossorochromis rostratus is notorious for being late bloomers, especially the male Fossos, often frustrating hobbyists who believe they have been unsuccessful in keeping them. This means it will take more attention and patience to wait for your fish to color up, or you might want to consider another species.

With that being said, if you can provide them with the right environment and diet, you’ll be rewarded with a beautiful fish that’s a great addition to any large Hap aquarium.

In this guide, we’ll go over everything you need to know about Fossos care, including their specie profiles, habitat, diet, growth rate, and more.

Species Profiles

Fossorochromis rostratus, more commonly known as Fossos and Malawi Sand Diver among hobbyists, are a type of cichlid native to Lake Malawi in Africa. Although it was first observed and recorded by Boulenger in 1898, we rarely hear about many cases of successful spawning in the home aquarium until the past ten years.

F. rostratusare is the only member in its genus. In the wild, they widespread distribute throughout the entire lake but are more commonly found near rocky shores and in areas with sandy substrates.

Although they are usually seen in large groups of up to 50 individuals with only one male showing dominant coloration, they are not considered a schooling fish. In Lake Malawi, seeing a school of 20 fish per square meter is ubiquitous.

The Fossorochromis rostratus is currently listed on the IUCN Red List as Least Concern (LC).

Scientific Name:Fossorochromis rostratus
Common Name:Fossos, Malawi Sand Diver
Care Level:Advanced
IUCN Red List:Least Concern (LC)
Origin:Lake Malawi, African
Lifespan:8 to 12 years
Max Size:16 inches (35 cm)
Temperature:77-84°F (25-29°C) 
PH:7.8 to 8.8
Water hardness:10 to 25 KH
Minimum Tank Size:125 gallons (72″ x 18″ x 21″)


male Fossos

Fossos have an evolved stocky and elongated body shape similar to other Haplochromine cichlids. Their dorsal and caudal fins are quite prominent and are mostly complemented by a blue hue. The anal and pectoral fins are very pointed as well. Thanks to the spines on their fins, making them look much bigger and menacing.

Generally, dominant males will take on metallic colorations, ranging from blue to yellow. The coloration will intensify when they are ready to spawn or forage in the morning. You may see faint vertical bars or irregular oval marks on the body.

Like the Big Mouth Hap, quite individual differences in coloration and pattern exist based on location. This is especially true with the dominant male.

Unfortunately, females, subdominant males, and juveniles are much more drab-colored than dominant males, taking on a subdued cream-yellow color. 

Like dominant males, they have five irregular dark markings down the flank, but the dark colors “bleed” onto the lighter cream body forming a checkerboard pattern.

Male or Female?

The Fossorochromis rostratus is a sexually dimorphic cichlid. Dominant males have a distinct appearance and are much more colorful than females and subdominant males. However, it can be tough to sex females and subdominant males as they look exactly the same, but you will be able to tell by venting them when they grow big.

When they are at least a year old, female Fossos will develop two holes of different sizes, one much larger than the other and used for reproduction. In comparison, males will have two holes of the same size. Check out this video and see for yourself.

Size & Growth Rate

The Fossorochromis rostratus is a relatively large species of cichlid, typically reaching up to 10 inches (25 cm) in length. In the wild, males can grow larger, up to 16 inches (35 cm). Fish in captivity usually stay on the smaller side.

The growth rate of Fossos is fairly faster than most Haps, but being late bloomers, they typically reach sexual maturity at 8 inches (20 cm) in 2.5 years. After that, its growth rate slows down and will take a year to get full adult size.

The dominant males don’t show their coloration until 6 inches. For this reason alone, don’t expect your fish to transform from a pale base to vibrant coloration overnight.

Fossorochromis rostratus Lifespan

When it comes to the lifespan of Fossorochromis rostratus, they can live up to 8-12 years with the proper care.

Many factors can affect a fish’s lifespan in captivity, such as water quality, diet, and stress. This goes for any species, no matter how hardy they are.

Malawi Sand Diver Care

Like any other haps, Fossos are not a fish for both beginners and intermediate cichlid keepers. Most of the difficulty with these fish comes from their aggression and requirements.

In the wild, Fossos are found over open sand areas in groups of females and subdominant males and may co-habit these patches with small groups of Cyrtocara moorii.

Fish from the open water sandy environment tend to be fast swimmers, and the Fossochromis rostratus is no exception. It requires a large aquarium with open areas and rocky caves. This is one of the reasons why this species is not for everyone, as you might have trouble getting a suitable habitat for them.

Fossos are usually not extremely aggressive in terms of aggression, but they can get towards each other if they don’t establish a hierarchy. Sometimes, the most dominant males might kill any other subdominant males.

If you’re up for the challenge, here are some basic care guidelines to get you started.

Fossorochromis rostratus Tank Size

Being an open water large cichlid, Fossos are accustomed to having plenty of room to swim and roaming over large areas in the wild.

I would recommend a tank size of at least 125 gallons (72″ x 18″ x 21″) for a group of 5-8 adult Fossos. If you plan on having a group of juveniles at the average purchased size (3.5 -5 inches), you can get away with a 75 gallons (48″ x 18″ x 21″) tank.

Water Parameters

Fossorochromis rostratus has similar water requirements to other Lake Malawi Cichlids. The lake’s water is alkaline and a bit warm.

Any species from the lake can tolerate salt slightly but can’t live in full brackish water. 

  • Water Temperature: 77-84°F (25-29°C)
  • pH Level: 7.8 to 8.8
  • Water Hardness: 10 to 25 dGH
  • Ammonia: 0 ppm
  • Nitrite: 0 ppm
  • Nitrate: <20 ppm

Avoid sudden changes to the water parameters as these fish are very sensitive to water changes. Stressed fish are susceptible to the disease “Malawi bloat.” 

Depending on your bio load, do water changes of 30-50% weekly for the sake of the fish and the aquarium. Poor water quality is the number one cause of death in cichlids, so take this seriously from day one.

Substrate & Rocks

Malawi Sand Diver, as its common name suggests, the fish spends a lot of time sifting through the sand for invertebrates and diving into the sand when scared.

Therefore, a soft sandy substrate is ideal. You can use medium-grain sand as long as there are no sharp objects that may scratch their mouths.

Unlike Mbunas, Fossos are not known to be rock-dwellers but rather open water swimmers. They need large areas to swim, so they don’t require an aquarium full of large piles of rocks. 

However, you should provide plenty of hiding places with rocks for brooding females and subdominant males. Also, stones that have sharp edges that could injure these fast-swimming fish.

Live plants are unnecessary; Fossos won’t eat them, but they will uproot them like other cichlids. Choose robust species such as Vallisneria if you want to add some green to the tank.

Diet & Food

The Fossorochromis rostratus is not a piscivore in the wild, feeding on invertebrates like insect larvae and small crustaceans caught by sifting mouthfuls of sand.

For juveniles, a staple diet should consist of high-quality spirulina flakes. Adults can be fed with quality cichlid pellets.

OSI Spirulina Flake Fish Food 7.06oz
  • Crude Protein minimum 41% Crude Fat minimum 4% Crude Fiber maximum 6% Moisture maximum 8% Vitamin A (min)...

You can incorporate live, frozen, or freeze-dried foods such as brine shrimp, bloodworms, and prawns. They really enjoy this kind of food!

Fossorochromis rostratus Tank Mates

In the wild, as I mentioned, the female Fossos shoal is in a large group with subdominant males while the dominant male swims around them in his own large territory.

The best tank mates for Fossos are more Fossos. It’s best to keep them in groups of 1-2 males with 3-6 females in a fairly large specie-only tank. Having 1-2 subdominant males will make the coloration of the dominant male more intense. But, once again, hiding places are a must for the subdominant males, or they will constantly be harassed.

Avoid keeping Fossos with boisterous Mbunas because Fossos are much larger and more aggressive than Mbunas. They are not known to eat Mbunas, like T. Macrostoma (Big Mouth Hap) but being an opportunistic feeder, they may eat smaller Mbunas when given a chance.

If you must keep Fossos with other cichlids, choose tank mates that are too large to be harassed and eaten by Fossors and can tolerate similar water parameters. A few examples of such fish are:


Like most African cichlids, Fossorochromis rostratus is one of the highly developed maternal mouthbrooders. However, breeding these fish in captivity is not easy as the Mbunas for two reasons.

First, the subdominant males of the species are almost indistinguishable from the females until they achieve sexual maturity size. It will take a long time to wait. Also, they are the less common African cichlids, so finding good quality specimens for breeding purposes can be difficult.

The second reason is that it’s nearly impossible to recreate their natural breeding environment unless you have huge tanks or keep them in indoor ponds. In nature, the dominant males often take up a territory and create massive crater nests. These nests are so large that they can be up to 1 meter in diameter and 0.5 meters deep.

This is not the case in home aquariums.

If you intend to breed Fossos, it’s best to buy a group of juveniles and allow them to grow together. This will give you the best chance of success in getting a pair.

It’s recommended to move the pair to a separate breeding tank with plenty of hiding places and a large flat rock. The breeding tank should have a sand substrate and water parameters that match the main tank as closely as possible.

They have the same spawning habits as other haps. The female will mouth brood the eggs (Up to 130 eggs) for 3-4 weeks and continue to guard them for two weeks until the fry are large enough to be released.

After that, the fry can be fed with newly hatched brine shrimp to boost their growth rate.

Closing Thoughts

Fossorochromis rostratus is a beautiful African cichlid that is perfect for the advanced Cichlid keeper who has the patience to wait for a group of juveniles to grow out.

These fish are sometimes available in online stores or professional breeders with a moderate price tag, but they are relatively costly for a bonded pair.

These cichlids are not the species that have been known to suddenly boost coloration like some others. Fossos take a little time to “come into their own,” but when they do, the results are stunning.

Thanks for reading, and feel free to leave me a comment if you have any questions.

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Jeff Colt

Jeff Colt

Hello, I'm Jeff- an aquarium enthusiast with over 25 years of experience caring for a wide array of tropical fish, including koi, goldfish bettas, cichlids and more! For me: Aquariums are like jello - there's always room for more!

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