Linn's Haplochromis (Nimbochromis linni)

A Malawi predator with a long-term space commitment

Linn's Haplochromis (Nimbochromis linni) is a large predatory cichlid endemic to Lake Malawi. Its appeal lies in the deliberate behaviour of an ambush hunter: this is a fish to watch around rockwork and open space, rather than a small addition to a peaceful community. FishBase records a maximum length of 25 cm total length, so the adult aquarium deserves attention before the fish is ordered. The small dispatch grades make the early stages manageable; they do not reduce the eventual space, filtration or compatibility commitment.

One purchase supplies one live fish of the selected size. The size choices are 4 - 5 cm, 6 - 7 cm, 7 - 9 cm and XL. The size you select is the size supplied, not the adult size. XL is a size label rather than a stated measurement, so ask about that grade if a numerical length is important to your plans. Sex is guaranteed only when the selected option explicitly states male or female. This Linn's Haplochromis listing has no sex-guaranteed option. Choose the grade that fits a prepared aquarium and its existing residents, and use the live size selector for the offer at the time of purchase.

The scientific name used here is Nimbochromis linni. Older trade wording may use Haplochromis linni, and Linn's Haplochromis remains the common name. Those labels refer to the identity of this fish, rather than a reason to treat it as a general community species. Its family is Cichlidae, and FishBase describes it as freshwater and demersal, with rocky and intermediate habitat records. It has been observed ambushing fish prey. That feeding behaviour is the starting point for choosing companions, arranging the aquarium and understanding what a quiet fish may be doing.

A suitable home combines hard, alkaline water, mature biological filtration, good oxygenation, substantial swimming space and secure cover. The overall project suits a keeper accustomed to Malawi cichlids, who can recognise bullying and respond before an animal loses condition. A first aquarium needs to become stable before any livestock arrives; a large predator also needs a stocking plan that remains workable as the other fish grow. It is much easier to decide where the adult fish will live at the beginning than to find emergency accommodation later.

As broad Malawi cichlid guidance, OATA gives 23–27°C, pH 8.0–8.6, general hardness 12–18°dH and carbonate hardness 10–15°dKH. These are group recommendations, not a measured optimum specific to this species. FishBase's environmental records are different in scope and are explained in the care section. Stability, a working filter and careful stocking matter alongside the readings. A tank that has the desired pH but detectable ammonia is not ready for a new fish.

Think of the purchase as an adult predator project from the outset. A fish that can be swallowed is at risk, and sharing Malawi water requirements alone does not establish a safe mixture. OATA's broad advice names other Malawi cichlids and some Synodontis catfish as possible companions for the group, with caution; it does not approve every species or every individual for this predator. Evaluate size, feeding needs, aggression, aquarium layout and a practical separation plan together.

There is no need to buy several individuals simply to fulfil an assumed shoaling requirement. Plan numbers of Linn's Haplochromis for the adult aquarium and the intended community. OATA discusses crowded Malawi communities in general, but that advice is not a prescription to buy fifteen large predators or to overfill a tank. Obtain a stocking assessment for the actual adult aquarium before planning a pair, a group or a mixed cichlid community.

If you are still choosing a direction for the aquarium, the African cichlid collection can help you compare different projects. Compare adult needs before appearance, and seek advice about the whole aquarium rather than a list of colourful fish in isolation. Linn's Haplochromis is most rewarding when its natural feeding behaviour, water requirements and eventual size are central to the design.

Before purchase, write down the aquarium dimensions, the species and sizes already kept, your recent water readings and the filter arrangement. These details let a stocking discussion address the actual home rather than an idealised tank. Consider who will maintain it during holidays and how water changes will be carried out as the fish grows. A regular routine that the household can sustain is part of providing a suitable adult home.

Build the aquarium around the adult fish

The adult length is a planning measurement, not a promise that every fish will reach the maximum. FishBase gives 25 cm total length, which includes the tail. A juvenile can occupy far less space while still having the same eventual requirements. Assess usable floor space, clear routes through the aquarium and the room available to turn around cover. A tall tank with a crowded base can offer impressive volume while leaving a large cichlid few comfortable ways to move.

OATA recommends at least 200 litres for a reasonable Malawi community in its general group sheet. That number is not a species-specific minimum for this 25 cm predator and should not be used as approval for an adult Linn's Haplochromis community. The actual stocking, adult fish sizes and footprint need an individual assessment. Buy as large an aquarium as is practical, as OATA advises, and settle the adult plan before treating a small grade as a temporary solution.

Make a simple layout plan showing swimming space, rocks, filter outlets and access for maintenance. The arrangement should give fish a way to move away from one another while leaving you able to see whether a resident is trapped or excluded. A complete wall of stone may hide fish effectively but remove much of the usable area. Aim for cover that works with open routes, and leave places where waste can be removed during a water change.

Secure rockwork with digging in mind. OATA notes that Malawi cichlids will often dig and rearrange substrate, so decorative piles should remain stable when sand shifts around them. Stability matters more than the height of a dramatic arrangement. Check the layout before livestock enters, including access around equipment and the way stones rest. If a fish undermines a support later, deal with the unsafe structure promptly and calmly rather than waiting for it to fall.

OATA suggests coral sand or similar substrate to help buffer Malawi water. Substrate is one part of water management, rather than proof that the chemistry will automatically remain suitable. Test the aquarium after it has settled and test replacement water as well. A material that affects buffering needs to be understood alongside the supply water and maintenance routine. Choose a layout you can keep clean without repeatedly dismantling the territories.

Plants should be chosen with realistic expectations. The broad Malawi guidance warns that digging will uproot planting and suggests hardy plants that attach to décor where plants are wanted. Leave room for fish to move and keep leaves from obstructing equipment. A planted appearance is optional; healthy water, stable structure and a workable stocking plan are the priorities. If planting continually loosens, improve its placement instead of relying on repeated replanting around a territorial fish.

• Assess adult swimming room before choosing a dispatch grade.
• Keep stones stable when substrate is displaced.
• Leave accessible areas for removing waste.
• Review the layout as fish grow and interactions change.

Mature filtration and oxygen before adding livestock

A mature biological filter is essential. RSPCA explains that fish release toxic ammonia, and that beneficial bacteria in a working filter convert ammonia to nitrite and then nitrate. Nitrite is also toxic. The presence of a filter does not itself demonstrate that this process is ready to handle the aquarium's feeding and livestock load. Check the water, understand how the filter was matured and make sure its operation is dependable before a new cichlid arrives.

Adding fish increases the waste the biological filter must process. OATA recommends increasing numbers slowly so the bacterial population can increase as fish and feeding are added. This is especially relevant when a small fish is joining an already busy aquarium: spare visual space does not necessarily mean spare biological capacity. Use the guide to preparing a first tropical aquarium for the general maturation principles, then apply a stocking plan appropriate to this larger Malawi species.

OATA recommends oversized filtration and strong aeration for crowded Malawi communities. Those are group recommendations, and they underline why water movement and maintenance deserve careful thought in a predator aquarium. Position equipment so circulation reaches the working areas of the tank without leaving waste in inaccessible corners. Follow the equipment maker's instructions, check for blockages and keep the filter operating reliably. Food and fish waste still require removal even when the filter is substantial.

Look at the water surface and the fish as well as the equipment. A running motor is only one indication of function; a blocked intake or dirty filter can reduce useful circulation. OATA lists changes in breathing and swimming among the observations that warrant attention. If fish gather at the surface, breathe differently or behave unusually, test the water and check circulation promptly. Ask for help when you cannot account for the change, rather than adding more livestock while the cause is unclear.

Plan how filtration will be maintained without losing its biological function. OATA advises lightly rinsing filter media in water removed during a partial water change, rather than washing it under the tap, because chlorine or chloramine can harm the beneficial bacteria. Keep cleaning focused on maintaining flow and removing accumulated debris. Treat biological media as a living part of the system, and follow the filter's maintenance guidance alongside the aquarium's test results.

Keep water recommendations and wild records separate

The routine aquarium figures used here come from OATA's broad African Malawi cichlid guidance: temperature 23–27°C, pH 8.0–8.6, general hardness 12–18°dH and carbonate hardness 10–15°dKH. Keep that group scope in mind when discussing an individual aquarium. The guidance is a practical starting point for a Malawi setup, not proof that any one reading within the range is the best possible value for every fish.

FishBase lists environmental values of 23–25°C, pH 7.0–8.5 and hardness 10–15°dH for Nimbochromis linni. These are species environmental records rather than a complete aquarium husbandry recipe. They should not be used to make abrupt changes to an established tank or combined with other sources to invent a wider target. The two sources describe different contexts; keeping that distinction makes the advice clearer than presenting one blended set of unexplained figures.

General hardness and carbonate hardness measure different aspects of the water. The OATA guidance gives separate values for each, so record each reading with its unit instead of treating hardness as one interchangeable number. Measure pH, temperature and the nitrogen compounds as well. The water chemistry guide explains the role of the tests and helps make a tank record useful when you seek advice.

Know what comes from the tap before deciding how the aquarium will be managed. Replacement water needs treatment to remove harmful chlorine or chloramine, as OATA recommends. Match routine replacement water sensibly to the established aquarium and avoid pursuing a perfect-looking figure with sudden adjustments. If the supply is very different from the intended Malawi conditions, settle a reliable preparation method before ordering livestock. An approach that can be repeated is more useful than a one-off reading achieved on the purchase day.

The water matcher can help compare measured readings with stated guidance. Use it alongside the context of those values and the actual aquarium's test history. A numerical match cannot assess predation risk, filtration maturity or whether the layout gives a large fish enough room. It is one aid within the decision, and its result should lead to a practical assessment of the whole setup.

Ammonia and nitrite should be zero mg per litre under OATA's guidance. For nitrate, OATA recommends that the aquarium level does not exceed normal tap-water levels by more than 20 mg per litre. This is a comparison with the supply, not a statement that every tap supply starts at zero. Record both values when assessing the maintenance routine. If waste readings rise, examine feeding, stocking, filter function and water changes rather than considering pH alone.

Feed a fish predator with measured aquarium foods

FishBase describes this species as piscivorous and records ambush predation on fish. That natural diet explains its risk to small companions. In the aquarium, use food suited to a larger predatory cichlid and obtain advice about the fish's grade and feeding history. OATA's broader guidance for more predatory Malawi cichlids supports pellets with a higher animal content and frozen aquatic foods such as brine shrimp, prawns or cockles. This is group feeding guidance, not a species-specific menu tested for every life stage.

Choose food pieces that the individual can take comfortably. A 4 - 5 cm fish and a much larger fish will not necessarily manage the same pellet or frozen portion. Observe actual feeding rather than assuming that the named food is suitable because its ingredients sound right. If a fish repeatedly mouths and drops an item, ask about a more appropriate size or presentation. Keep portions controlled so feeding supplies the fish without leaving a large amount of organic waste in the aquarium.

OATA suggests feeding Malawi cichlids twice daily, only as much as they consume within a few minutes. Use that as broad guidance and adjust the amount to observed intake, condition and water quality. Feeding the aquarium is not the same as seeing this particular fish eat. Watch whether it reaches food, whether a more assertive resident takes everything first and whether any pieces settle behind the rocks. Uneaten food breaks down and adds to the filter's burden.

A predatory fish does not need smaller aquarium residents supplied as food to make the setup interesting. Its presence already requires careful protection of unsuitable companions. Use appropriate prepared and frozen aquarium foods as the practical feeding approach, and seek advice if the fish does not accept them after settling. Avoid making a feeding problem into a stocking problem by adding animals that may be prey. A successful routine is one you can observe, measure and maintain.

Keep a brief feeding record when introducing a new fish or changing food. Note what it accepts, whether it gets its share and any change in condition. This helps distinguish refusal from competition and lets you discuss the problem more clearly. Do not compensate for a missed meal by leaving excessive food in the water. If appetite falls alongside unusual breathing, hiding or a change in swimming, test the aquarium and ask for guidance on the whole situation.

Maintain the tank and recognise changes early

OATA recommends a weekly partial water change of 25% as general Malawi maintenance guidance, with a siphon to remove solid waste. Treat this as a starting routine to assess against your own readings and stocking. A large fish community may create more waste than expected, and the correct response is to evaluate the system rather than assuming one schedule guarantees clean water. Prepare conditioned replacement water and keep the process calm around established territories.

Test at least weekly, as the OATA sheet recommends, and check more promptly when behaviour changes or after a stocking or feeding adjustment. A dated record is easier to interpret than a remembered impression that the water has always been fine. Include ammonia, nitrite and nitrate, plus the relevant chemistry and temperature. Watch for trends as well as individual readings. Consistently rising nitrate or reduced filter flow gives you an opportunity to act before the aquarium becomes difficult to manage.

Use the maintenance session to inspect equipment and the layout. Check filter intakes for debris, verify that rockwork remains stable and look for places where waste accumulates. Keep open routes usable as the fish grow. A shelter that worked for a juvenile may become an awkward narrow gap later, so review the arrangement as part of adult planning. Changes should solve a specific practical problem while maintaining the overall space and cover the fish depend on.

Observe the fish's normal behaviour once it has settled. OATA highlights changes in swimming, colour, aggression, breathing, appearance, body condition and feeding as possible signs of trouble. A fish that is suddenly much more withdrawn or repeatedly prevented from feeding needs attention even if no obvious mark is visible. Look at the surrounding fish and water readings together. The pattern of what changed often provides more useful information than one isolated observation.

If you see white spots, fluffy growth, fin or scale damage, altered breathing or loss of condition, test the water and contact an experienced retailer for guidance. Keep details of when the change began and what recently happened in the tank. This guide does not supply a disease treatment recipe. Avoid choosing a treatment solely from a photograph or treating the whole tank without considering chemistry, equipment and the other residents. Early, specific advice is more useful than repeated guesses.

Receiving and introducing the fish

Have the aquarium stable and ready before the delivery day. Tropical Fish Co's policy describes hand-bagging with pure oxygen, an insulated polystyrene box and a heat pack when weather requires it. Tracking and the confirmed delivery date are supplied by email, and the parcel travels with a licensed live-animal courier. Arrange for someone to receive it at the address, because live fish cannot be left unattended. Follow the date confirmed for your order rather than planning around an assumed dispatch interval.

Open and inspect the parcel on the day it arrives. Record one continuous unboxing video beginning with the still-sealed parcel and visible outer box, then show the opening and the fish still in its sealed bag. Keep the order number available and contact the shop the same day if there is an arrival problem. This evidence helps resolve an arrival claim; it is separate from the aquarium preparations that support the fish afterwards.

The supplied store guidance says to acclimatise slowly and float the bag for 20–30 minutes before release. Do not pour bag water into the aquarium. Prepare everything you need before starting so the fish can be introduced calmly. Once it is in the tank, observe how it uses cover and how the residents respond, rather than assuming the introduction has succeeded simply because the bag is empty.

OATA recommends checking that ammonia and nitrite are zero before adding fish and making stocking increases gradually. Keep this principle in mind even when the new arrival is small. Observe feeding and condition as it settles, and pay particular attention to exclusion from space or food. If the existing residents repeatedly target it, be ready to act on the separation plan you made before purchase. An arrival guarantee and a compatible long-term aquarium solve different problems.

Read the current delivery and Live Arrival Guarantee policy before ordering so the receiving and claim requirements are clear. The policy explains the confirmed delivery arrangements and how to contact the team if something has gone wrong. Keep those practical arrangements organised alongside the aquarium preparation, allowing you to focus on the fish when the parcel arrives.

Choose companions by adult size and behaviour

The clearest species-specific compatibility fact is that Nimbochromis linni eats fish and has been observed ambushing prey. Small companions are therefore a serious risk, even when the predator seems quiet or was initially smaller. A fish that is safe beside a juvenile may become vulnerable as the predator grows. Assess the anticipated adult relationship and review it during growth; present-day calm does not establish a permanent arrangement.

OATA's broad Malawi guidance restricts possible mixtures to other Malawi cichlids and some Synodontis catfish, and emphasises caution. Treat these as categories to assess, not a list of guaranteed companions. Similar water needs are necessary but do not resolve size differences, feeding competition or aggression. Ask for advice about the exact species and sizes already in the tank, the adult footprint and what you will do if an individual fails to settle.

Malawi cichlids can be aggressive, and OATA recommends planning stocking order and introducing more peaceful species before more aggressive ones. The same sheet discusses adding fish in groups to avoid isolating a target during settlement. Those are broad community-management principles, not an instruction to add an arbitrary group of Linn's Haplochromis. Any addition needs enough space and mature filtration for its increased load, with the predatory nature of this species considered separately.

Watch for practical signs that a mixture is failing. A fish constantly confined to one corner, repeatedly driven away from food or unable to use cover is not benefiting from a large nominal tank volume. OATA includes changes in aggression and hiding among warning signs. Deal with the interaction before an excluded fish loses condition. Have a workable way to separate animals, and seek advice if changing the layout or stocking does not resolve the pressure.

Rockwork can help break sight lines, but it cannot make a prey-sized fish safe. OATA notes that rearranging décor may reduce territorial aggression as fish establish new territories. Use that approach thoughtfully where appropriate, checking stability after any move. Keep the requirements of all residents in view: adequate open room, access to food and places to move out of sight. Avoid rebuilding the entire aquarium repeatedly without understanding which interaction is causing the problem.

Numbers, sex and the limits of community advice

Plan numbers individually for the adult aquarium. Linn's Haplochromis should not be treated as a schooling fish with a required six-fish shoal. The number that can be kept must be assessed for the adult aquarium, the other residents and the keeper's ability to manage conflict. One fish is the unit sold here; that unit is not itself a recommendation that every aquarium should contain only one or that a pair will automatically get along.

OATA describes Malawi communities of at least fifteen fish with slight crowding to spread aggression. That is group-level guidance across a diverse set of Malawi cichlids, not a species-specific target for fifteen large fish predators. It also requires filtration, oxygen and a suitable community plan. Do not apply the number mechanically to this species or use it to justify adding livestock beyond what the aquarium can accommodate. Adult size and predation remain decisive.

The OATA sheet also discusses keeping more females than males where appropriate in Malawi communities. This offer has no sex-guaranteed option, so a purchase should not be used to promise a breeding pair or a particular sex ratio. Do not infer the supplied fish's sex from a gallery image or assume a juvenile grade will resolve into the planned group. If a stocking plan depends on sex, discuss a suitable explicitly sexed offer before committing.

A well-managed aquarium is judged by the fish living in it, not just the care figures shared by its residents. Monitor access to food, freedom to move and the ability to rest without persistent harassment. Reassess the community when fish grow, when an individual becomes more assertive or when a new fish changes the balance. A plan that includes observation and practical alternatives gives this predator a better chance of fitting a suitable Malawi project.

Practical questions before purchase

How big does Linn's Haplochromis get?

FishBase records a maximum of 25 cm total length, including the tail. Plan the aquarium around a large adult cichlid rather than the smaller dispatch grade, and assess usable swimming room and the other residents before purchase.

What size aquarium does Linn's Haplochromis need?

It needs a spacious adult aquarium with secure rockwork, open routes, mature filtration and good oxygenation. OATA's general 200-litre Malawi community figure is not a species-specific minimum for this large predator. Ask for a stocking assessment based on the footprint and intended adult residents.

How many Nimbochromis linni should I keep together?

Plan the number for the adult aquarium and its other residents. OATA's general discussion of crowded Malawi communities is not a recommendation to keep fifteen of these large predators. Assess numbers individually for the adult aquarium, the other fish and a practical separation plan.

Does Linn's Haplochromis suit a beginner?

Its large adult size, predation risk and Malawi community management needs make it a demanding first fish. It is better approached by a keeper comfortable with mature filtration, hard alkaline water, careful stocking and recognising when an individual is being bullied or excluded from food.

What should I feed Nimbochromis linni?

It is a fish predator. For aquarium feeding, OATA's broader advice for predatory Malawi cichlids supports pellets with higher animal content and suitable frozen aquatic foods such as brine shrimp, prawns or cockles. Match the portion and food size to the individual and remove uneaten food.

What temperature and pH does Linn's Haplochromis need?

OATA's broad Malawi aquarium guidance is 23–27°C and pH 8.0–8.6, with general hardness 12–18°dH and carbonate hardness 10–15°dKH. These are group recommendations, not a species-specific optimum. FishBase's environmental records have a different scope and should not be blended into a wider aquarium target.

Is it aggressive or likely to nip fins?

Malawi cichlids can be aggressive, and this species adds a fish-predation risk. The practical concern includes chasing, exclusion and swallowing smaller fish rather than only fin nipping. Watch whether every resident can use space and obtain food, and separate animals if the mixture is failing.

Which other animals can it live with?

OATA's general Malawi guidance names other Malawi cichlids and some Synodontis catfish as possibilities to assess with caution. No category guarantees compatibility with this predator. Evaluate the exact species, adult sizes, feeding needs, temperament and layout; small fish that may become prey are unsuitable.

How does the fish arrive alive in the UK?

Tropical Fish Co's delivery policy describes oxygen-filled bags, an insulated box, weather-appropriate heat packing and a licensed live-animal courier. Be present to receive the parcel and inspect it the same day. Record continuous unboxing from the sealed parcel to the fish still in its sealed bag and contact the shop that day.

Further reading and the scope of this guidance

FishBase: Nimbochromis linni supplies the species identity, family, Lake Malawi distribution, recorded 25 cm total length, rocky and intermediate habitats and fish-predation observations. Its environmental figures describe the species record and are kept separate from routine aquarium recommendations.

OATA: looking after African Malawi cichlids supplies broad UK guidance on water, filtration, aeration, maintenance, feeding and cautious community planning. Malawi cichlids differ in adult size and behaviour, so this group advice should be used with an individual aquarium assessment. Community volume and stocking numbers in the sheet are not species-specific requirements for this fish.

RSPCA: the aquarium environment explains why working biological filtration matters and how ammonia, nitrite and nitrate relate to waste processing. These principles apply to the aquarium system rather than establishing a special numerical requirement for Linn's Haplochromis.

The species overview for Nimbochromis linni provides supplementary natural-history context, including Lake Malawi endemism and the recorded adult length. The species name honours D. Wayne Linn. Consult the care recommendations in their own context, and seek advice about the fish and aquarium you intend to keep rather than assuming that a natural-history description is a complete husbandry plan.