Upside-Down Catfish Care Guide – Tank Setup, Feeding and Breeding

Quick summary

The Upside-Down Catfish is an easy-to-keep, peaceful catfish suited to beginners, thriving in community tanks of 75 litres or more when kept in groups of four to six. It’s hardy and adaptable to a range of water conditions, though breeding it successfully is difficult and best left to experienced keepers.

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In this guide:

Introduction
Quick Stats
Appearance
Natural Habitat
Tank Size and Setup
Water Parameters
Filtration and Equipment
Diet and Feeding
Behaviour and Temperament
Tank Mates
Breeding
Common Diseases
FAQs

Introduction

The Upside-Down Catfish (Synodontis nigriventris) is one of the most fascinating freshwater fish available in the aquarium hobby. As its name suggests, this small African catfish spends the vast majority of its time swimming in an inverted position – belly facing upward – a behaviour that has captivated fishkeepers for decades. While several species of Synodontis occasionally swim upside down, S. nigriventris is unique in that it adopts this posture almost permanently, feeding, resting, and navigating its environment in this distinctive orientation.

This species has been known to science since 1936, when it was described by the ichthyologist David. However, the behaviour of upside-down swimming catfish was noted by ancient Egyptians thousands of years ago, with depictions appearing in tomb paintings dating back nearly 4,000 years. Whether those ancient illustrations depict S. nigriventris specifically or a related species is a matter of scholarly debate, but the cultural significance of these unusual fish is undeniable.

What makes S. nigriventris particularly remarkable from a biological standpoint is its reversed countershading. Most fish have dark backs and pale bellies, a camouflage strategy that helps them blend in when viewed from above (against the dark depths) or below (against the bright surface). Because S. nigriventris swims upside down, its colouration is reversed: the belly is darker than the back. This adaptation provides the same camouflage benefits but is oriented for a life lived inverted. It is a striking example of how behaviour and morphology co-evolve.

In the aquarium, the Upside-Down Catfish is a peaceful, hardy, and endlessly entertaining species. It is well suited to community tanks, adapts to a range of water conditions, and can be kept by beginners and experienced aquarists alike. Its modest adult size, typically around 7 to 10 centimetres, means it does not require an enormous tank, and its sociable nature means it thrives in small groups. This guide covers everything you need to know to keep Synodontis nigriventris healthy, comfortable, and displaying its full range of natural behaviours.

Quick Stats

Scientific name	Synodontis nigriventris
Common names	Upside-Down Catfish, Blotched Upside-Down Catfish
Family	Mochokidae
Origin	Central Africa – Congo River basin (Democratic Republic of the Congo, Republic of the Congo, Cameroon)
Adult size	7 – 10 cm
Lifespan	5 – 15 years
Difficulty	Easy
Breeding difficulty	Difficult
Temperature	22 – 28 °C
pH range	6.0 – 7.5
General hardness (GH)	4 – 15 dGH
Carbonate hardness (KH)	3 – 12 dKH
Minimum tank size	75 litres
Conservation status	Least Concern (IUCN)

Appearance

Synodontis nigriventris has a compact, somewhat flattened body shape typical of many Synodontis species, with a broad head, large eyes, and three pairs of barbels around the mouth. The maxillary barbels (the upper pair) are the longest and are often branched, a characteristic feature of the Mochokidae family. The mandibular barbels (lower pairs) are shorter and also branched, giving the fish a distinctive whiskered appearance that aids in foraging along surfaces.

The most immediately striking aspect of this fish’s appearance is its reversed countershading. The ventral surface (belly) is noticeably darker than the dorsal surface (back), the opposite of what is seen in the overwhelming majority of fish species. The base colouration is a light brown to greyish-tan on the dorsal side, overlaid with irregular dark brown or blackish blotches and spots that provide excellent camouflage among roots, driftwood, and leaf litter. The belly ranges from dark brown to almost black, sometimes with a slightly mottled pattern. This reversed colouration is an adaptation to the fish’s inverted swimming posture, ensuring it remains camouflaged when viewed from below against the water surface or from above against the substrate.

The fins are translucent to lightly pigmented, often bearing faint spotting or banding that matches the body patterning. The dorsal fin features a strong, serrated leading spine – a defensive adaptation common across the Synodontis genus. Care should be taken when netting this species, as the spines can easily become entangled in fine mesh. The adipose fin is present and relatively prominent. The caudal fin is forked, and the pectoral fins also possess robust leading spines.

Sexual dimorphism is subtle. Mature females tend to be slightly larger and noticeably rounder in the body when viewed from above, particularly when gravid. Males are generally slimmer and may be marginally smaller. Distinguishing the sexes with certainty can be challenging outside of breeding condition.

Juvenile fish display the same basic colouration pattern as adults, though the blotching may be slightly more pronounced or contrasting in young specimens. The reversed countershading develops early and is already apparent in juveniles that begin adopting the inverted swimming posture at around seven to eight weeks of age.

Natural Habitat

Synodontis nigriventris is native to the Congo River basin in Central Africa, with its range spanning parts of the Democratic Republic of the Congo, the Republic of the Congo, and Cameroon. It inhabits slow-moving tributaries, densely vegetated backwaters, and shallow, shaded areas of rivers and streams where overhanging vegetation, submerged roots, and floating plants provide abundant cover.

In its natural environment, this species is typically found in areas with soft, slightly acidic to neutral water. The substrate in these habitats tends to be sandy or muddy, with a thick layer of fallen leaves and decaying organic matter. Tangles of driftwood, root systems, and dense aquatic or marginal vegetation are common features, providing the shaded retreats that S. nigriventris favours. The water is often tannin-stained and relatively dim, filtered through canopy cover and enriched by decomposing plant material.

The upside-down swimming behaviour is thought to have evolved in part as an adaptation to feeding on the underside of submerged logs, branches, and broad-leaved plants, where algae, biofilm, insect larvae, and other invertebrates accumulate. By swimming inverted, the fish can graze these surfaces efficiently without needing to contort its body. The reversed countershading then evolved as a consequence of this habitual posture, providing camouflage appropriate to a life spent belly-up.

S. nigriventris is a gregarious species in the wild, typically found in loose groups rather than as solitary individuals. It is primarily crepuscular and nocturnal, becoming most active during dawn, dusk, and nighttime hours, though aquarium specimens often adapt to daytime activity, particularly during feeding.

Tank Size and Setup

A minimum tank size of 75 litres is recommended for a small group of Upside-Down Catfish. Because this is a social species that displays more natural behaviour and reduced stress when kept in groups of at least four to six individuals, a tank of 100 to 150 litres is preferable for a comfortable shoal. Larger tanks also offer greater scope for aquascaping and the inclusion of suitable tank mates.

The aquascape should be designed to replicate the shaded, structurally complex habitats that S. nigriventris occupies in the wild. Driftwood is arguably the single most important element, as the fish will spend considerable time resting inverted beneath branches, logs, and overhangs. Provide several pieces of driftwood arranged to create caves, overhangs, and sheltered nooks. Bogwood and Malaysian driftwood are excellent choices, as they also release tannins that soften the water and create the slightly acidic, tea-coloured conditions reminiscent of the species’ natural habitat.

Rock formations can supplement the driftwood, creating additional hiding spots. Slate, smooth river stones, and inert rocks stacked to form caves and crevices work well. Ensure all rock structures are stable and cannot collapse, as the catfish will wedge themselves into tight spaces.

Live plants are highly recommended. Broad-leaved species such as Anubias and Java Fern are particularly suitable, as the catfish will graze algae and biofilm from the underside of their leaves while swimming inverted – a behaviour that is endlessly entertaining to observe. These plants also thrive when attached to driftwood, making them easy to incorporate into the aquascape. Floating plants such as Amazon Frogbit, Water Lettuce, or Salvinia are also excellent additions, as they dim the lighting and provide the subdued conditions that encourage daytime activity.

The substrate can be sand or fine gravel. Sand is preferable, as it is gentler on the fish’s barbels and more closely replicates natural conditions. A dark-coloured substrate will help the fish feel secure and may enhance their colouration.

Lighting should be moderate to subdued. S. nigriventris is naturally a shade-loving species, and excessively bright lighting will cause the fish to remain hidden for extended periods. If brighter lighting is needed for plant growth, floating plants and tall-growing stem plants can be used to create shaded zones within the tank.

Ensure the tank has a secure lid. While Upside-Down Catfish are not prolific jumpers, their tendency to swim near the water surface, particularly when feeding on the underside of floating objects, means that accidental escapes are possible if the tank is left open.

Water Parameters

Synodontis nigriventris is a robust and adaptable species that tolerates a relatively broad range of water conditions. Nonetheless, maintaining stable parameters within its preferred range will promote optimal health, colouration, and longevity. The following table summarises the recommended water parameters for this species.

Temperature	22 – 28 °C
pH	6.0 – 7.5
General hardness (GH)	4 – 15 dGH
Carbonate hardness (KH)	3 – 12 dKH
Ammonia	0 ppm
Nitrite	0 ppm
Nitrate	Below 20 ppm

The ideal temperature for most community setups is around 24 to 26 °C, which sits comfortably within the range tolerated by the majority of suitable tank mates. Avoid sudden temperature fluctuations, as these can stress the fish and increase susceptibility to disease. A reliable heater with a thermostat is essential unless the ambient room temperature consistently falls within the acceptable range.

Slightly acidic to neutral water (pH 6.5 to 7.0) is ideal and replicates the conditions found in the species’ native Congo basin tributaries. The addition of driftwood and dried Indian Almond leaves (Catappa leaves) can help naturally lower pH and add beneficial tannins. However, S. nigriventris is adaptable and will generally do well in moderately alkaline water up to pH 7.5, provided other conditions are stable.

Ammonia and nitrite must always remain at zero. These compounds are toxic to all fish and indicate an insufficiently cycled or overloaded filtration system. Nitrate should be kept below 20 ppm through regular partial water changes. Weekly water changes of 20 to 30 per cent are a good baseline, though the exact frequency and volume will depend on stocking density, feeding regime, and filtration capacity.

Filtration and Equipment

A good quality filter rated for the tank volume is essential. Synodontis nigriventris is not an especially messy species for its size, but it does produce a moderate bioload, particularly when kept in the recommended groups of four to six or more. An external canister filter or a well-sized internal power filter will provide adequate mechanical, biological, and chemical filtration for most setups. Sponge filters are also suitable, especially in smaller tanks or breeding setups, and have the added benefit of providing a surface for biofilm growth that the catfish may graze.

Water flow should be gentle to moderate. In the wild, S. nigriventris inhabits slow-moving waters, and excessively strong currents can cause stress and make it difficult for the fish to maintain its inverted posture comfortably. If using a powerful canister filter, consider using a spray bar or lily pipe to diffuse the outflow and reduce the current strength. Positioning the filter outlet so that it creates calm zones within the tank, particularly near favoured resting spots, is advisable.

An adjustable aquarium heater with a reliable thermostat is necessary to maintain stable temperatures. Choose a heater rated appropriately for the tank volume – typically 1 watt per litre is a reasonable guideline, though this varies with ambient room temperature. A separate thermometer (digital or glass) should be used to verify the heater’s accuracy.

Lighting should be moderate. LED fixtures with adjustable brightness or dimmable settings are ideal, as they allow you to create the subdued conditions this species prefers without sacrificing plant growth. A timer set to provide 8 to 10 hours of light per day will establish a consistent photoperiod and encourage a natural activity cycle.

An air pump is not strictly necessary if the filter provides adequate surface agitation for gas exchange, but it can be a useful addition in warmer months when dissolved oxygen levels may drop. A fine airstone positioned away from the main resting areas will provide supplementary oxygenation without creating excessive disturbance.

Diet and Feeding

Synodontis nigriventris is an omnivore with a broad and undemanding diet. In the wild, it feeds on a variety of food sources including algae, biofilm, insect larvae, small crustaceans, worms, and plant matter. Its upside-down swimming habit is closely linked to its feeding strategy: by swimming inverted, it can efficiently graze the underside of submerged wood, rocks, and leaves where food accumulates. It also feeds from the water surface in its inverted posture, scooping up floating food items and surface-dwelling insects.

In the aquarium, a varied diet should be offered to ensure nutritional completeness. High-quality sinking pellets or wafers formulated for omnivorous catfish should form the staple of the diet. These foods sink to the substrate or rest on surfaces where the catfish can find them during their active periods. However, S. nigriventris also readily accepts floating foods, which it takes from the surface while swimming upside down – a behaviour well worth observing.

Supplement the staple diet with live or frozen foods such as bloodworm, daphnia, brine shrimp, mosquito larvae, and tubifex. These protein-rich foods promote good growth, colouration, and breeding condition. Blanched vegetables such as courgette (zucchini), cucumber, and shelled peas provide valuable plant-based nutrition and fibre. Spirulina-based flakes or wafers are another excellent supplement.

Feed once or twice daily, offering only as much food as the fish can consume within a few minutes. Because S. nigriventris is primarily crepuscular and nocturnal, feeding in the evening or shortly after lights-out can be beneficial, as the fish will be more active and responsive. That said, aquarium-adapted specimens often learn to feed readily during the day, particularly if they associate the keeper’s approach with food.

Avoid overfeeding, as uneaten food will decompose and degrade water quality. Remove any uneaten vegetables or large food items after a few hours to prevent fouling.

Behaviour and Temperament

The defining behavioural characteristic of Synodontis nigriventris is, of course, its inverted swimming posture. Unlike other Synodontis species that may occasionally flip upside down to feed from the surface or the underside of objects, S. nigriventris adopts this posture as its default orientation. It rests upside down beneath driftwood, leaves, and overhangs; it swims upside down through open water; and it feeds upside down at the surface and on submerged surfaces. The fish is perfectly capable of swimming in the conventional orientation and will sometimes do so, particularly when startled or when navigating rapidly between hiding spots, but the inverted posture predominates.

This species is peaceful, retiring, and non-aggressive. It poses no threat to other fish of similar or larger size and generally ignores its tank mates entirely. It is not territorial in the conventional sense, though individuals may have preferred resting spots beneath a particular piece of driftwood or within a specific cave. Minor squabbles over hiding spots can occur, but these are brief and harmless, resolved through gentle nudging rather than any form of aggression.

S. nigriventris is a social species that is most comfortable and displays the most natural behaviour when kept in groups. A minimum group of four is recommended, with six or more being ideal. Solitary individuals or pairs tend to be excessively shy, spending almost all of their time hidden and rarely venturing out, even at feeding time. In a group, the fish gain confidence from the presence of conspecifics and are far more likely to be active and visible, including during daylight hours.

Activity levels peak during the crepuscular and nocturnal periods. At dawn and dusk, groups of Upside-Down Catfish can be observed swimming together through the midwater and upper water column, often in their characteristic inverted posture, creating a truly unique spectacle. During the brightest part of the day, they tend to retreat to their preferred hiding spots, clustering together beneath driftwood or inside caves. Subdued lighting, floating plants, and ample cover encourage greater daytime activity.

The fish are generally quiet and unobtrusive, but like many Synodontis species, they can produce audible sounds by stridulating their pectoral fin spines. This is typically heard when the fish are handled or netted and is a stress or defensive response rather than a normal communication behaviour.

Tank Mates

The peaceful and retiring nature of Synodontis nigriventris makes it an excellent community fish. It coexists well with a wide range of similarly sized, non-aggressive species. Because it occupies primarily the mid to upper water column (thanks to its inverted swimming habit) and retreats to sheltered spots near the bottom during rest periods, it does not compete heavily for space with most community fish. The best tank mates are peaceful species that thrive in similar water conditions and will not harass or outcompete the catfish. Avoid large, aggressive, or predatory species that may view the small catfish as prey, and avoid very small fish or fry that the catfish might consume, as S. nigriventris is an opportunistic omnivore.

Good tank mates

Congo Tetra – A fellow Congo basin native that shares similar water parameter preferences, creating a biotope-appropriate pairing.
Cherry Barb – A peaceful, similarly sized schooling fish that occupies the mid-water zone without competing for hiding spots.
Kribensis – Another West/Central African species that coexists peacefully, provided the tank offers sufficient caves for both species.
Harlequin Rasbora – A gentle schooling fish that thrives in soft, slightly acidic water, complementing the catfish perfectly.
Bristlenose Pleco – A peaceful bottom-dweller that occupies a different niche and rarely interacts with S. nigriventris.
African Butterfly Fish – A surface-dwelling species from similar African habitats that creates an interesting biotope pairing and occupies different tank zones.
Corydoras sterbai – A peaceful bottom-dwelling catfish that stays out of the Upside-Down Catfish’s preferred inverted resting areas.
Rummy-Nose Tetra – A calm, tightly schooling tetra that adds movement to the midwater without causing stress.

Fish to avoid

Oscar – A large, predatory cichlid that would view S. nigriventris as potential prey and create a dangerously stressful environment.
Jack Dempsey – A highly aggressive and territorial cichlid far too combative for cohabitation with this peaceful catfish.
Red-Bellied Piranha – An aggressive predator that poses an obvious lethal threat to small catfish.
Green Terror – A large, aggressive South American cichlid whose territorial behaviour would overwhelm the retiring S. nigriventris.
Tiger Barb – A notorious fin nipper that may harass slower-moving catfish, particularly targeting their barbels and fins.
African Pike Cichlid – A predatory ambush hunter that would readily consume fish of this size.
Red Devil Cichlid – An extremely aggressive and large cichlid completely incompatible with peaceful community species.
Bucktooth Tetra – Despite its small size, this species is a scale eater and would harass and injure the catfish.

Breeding

Breeding Synodontis nigriventris in captivity is achievable but considered difficult. Spontaneous spawning in well-maintained community tanks is occasionally reported, but deliberate breeding requires careful conditioning, appropriate setup, and some patience. The species is an egg scatterer, and parental care is minimal to nonexistent.

To attempt breeding, start by conditioning a group of healthy adults with a protein-rich diet of live and frozen foods such as bloodworm, brine shrimp, and daphnia over a period of two to four weeks. Females in breeding condition will appear noticeably rounder when viewed from above. A breeding group with a higher ratio of males to females (two or three males to each female) can increase the likelihood of spawning.

Set up a dedicated breeding tank of at least 60 to 75 litres with soft, slightly acidic water (pH 6.0 to 6.5, GH 4 to 8 dGH) at a temperature of 26 to 28 °C. Include spawning surfaces such as flat rocks, broad-leaved plants, or PVC pipes and clay pots turned on their sides. A sponge filter provides gentle filtration without posing a risk to eggs or fry. Dim the lighting and provide plenty of cover to reduce stress.

Spawning can sometimes be triggered by simulating the onset of the rainy season: perform a large (50 per cent) water change with slightly cooler, softer water, and increase aeration. Some breeders also report success with gradually lowering and then raising the water level over several days to mimic seasonal flooding patterns. Spawning typically occurs in the evening or overnight.

The female deposits eggs in sheltered locations – on the underside of flat surfaces, inside caves, or among plant leaves. Clutch sizes are variable but typically range from 100 to 450 eggs. The eggs are adhesive and relatively small. The adults should be removed after spawning, as they will readily consume the eggs if given the opportunity.

Eggs hatch in approximately two to three days at 26 to 28 °C. The fry are initially tiny and will absorb their yolk sacs over the following two to three days before becoming free-swimming. First foods should be infusoria, liquid fry food, or very fine powdered food, graduating to freshly hatched brine shrimp nauplii as the fry grow. The fry begin to exhibit the characteristic upside-down swimming behaviour at around seven to eight weeks of age, initially intermittently and then with increasing frequency as they mature.

Growth is relatively slow compared to many tropical fish, and it may take 12 to 18 months for juveniles to reach a size suitable for introduction to a community tank. Maintain excellent water quality in the rearing tank with frequent small water changes, and ensure there is no competition from larger or more aggressive fry.

Common Diseases

Synodontis nigriventris is a hardy species with no unique species-specific diseases, but it is susceptible to the common ailments that affect all freshwater aquarium fish. Good husbandry – stable water parameters, a varied diet, and a stress-free environment – is the best defence against disease.

Ich (white spot disease), caused by the protozoan parasite Ichthyophthirius multifiliis, is one of the most common diseases encountered in freshwater aquaria. It presents as small white spots resembling grains of salt on the body and fins, accompanied by flashing (rubbing against surfaces) and lethargy. Treatment involves raising the temperature to 28 to 30 °C and adding aquarium salt or a proprietary ich medication. Note that Synodontis catfish, like many scaleless or reduced-scale fish, can be sensitive to certain medications, particularly those containing copper or malachite green. Always use medications at half the recommended dose initially and monitor the fish closely.

Bacterial infections can occur as a secondary consequence of poor water quality, physical injury, or stress. Symptoms include reddened areas on the body or fins, fin erosion, ulcerations, or abnormal mucus production. Treatment involves improving water quality as a priority and, if necessary, using a broad-spectrum antibacterial medication suitable for scaleless fish.

Fungal infections (saprolegniasis) appear as white, cotton-like growths on the body, fins, or barbels. They often arise secondary to physical damage or in immunocompromised fish. Antifungal medications and improved water conditions are the standard treatment approach.

Barbel erosion is a condition sometimes seen in catfish kept over rough or sharp substrates or in tanks with poor water quality. The barbels become shortened, frayed, or eroded, impairing the fish’s ability to forage. Prevention is straightforward: use a soft, sandy substrate and maintain excellent water quality. Barbels can regenerate over time once conditions are improved.

Internal parasites may occasionally affect wild-caught or poorly quarantined specimens. Symptoms can include weight loss despite a good appetite, bloating, white or stringy faeces, and lethargy. Antiparasitic medications formulated for internal parasites can be administered through medicated food.

Stress is the underlying factor behind many disease outbreaks. Ensure that S. nigriventris has adequate hiding places, is kept in a group, is not bullied by tank mates, and is not subjected to sudden changes in water parameters. A stressed fish has a compromised immune system and is far more susceptible to opportunistic infections.

FAQs

Why does my Upside-Down Catfish swim upside down?

Swimming inverted is completely normal and healthy behaviour for Synodontis nigriventris. It is not a sign of illness, swim bladder disorder, or distress. This species has evolved to swim in an inverted posture almost permanently, and its reversed countershading (dark belly, lighter back) is a direct adaptation to this lifestyle. The behaviour likely evolved to facilitate feeding on the underside of submerged surfaces such as driftwood, rocks, and leaves, where algae, biofilm, and invertebrates accumulate. If your Upside-Down Catfish is swimming inverted, eating well, and behaving actively, it is perfectly healthy.

How many Upside-Down Catfish should I keep together?

Synodontis nigriventris is a social species that should ideally be kept in groups of at least four to six individuals. Solitary specimens or pairs tend to be extremely shy, spending virtually all of their time hidden and rarely emerging, even for food. In a group, the fish gain confidence and are significantly more active and visible. Groups also display more natural social behaviours, including loose shoaling during their active periods at dawn and dusk. If space permits, larger groups of eight or more create an even more impressive display.

Can Upside-Down Catfish be kept with shrimp?

This depends on the size of the shrimp. Synodontis nigriventris is an opportunistic omnivore and will eat anything small enough to fit in its mouth. Very small shrimp such as Cherry Shrimp (Neocaridina davidi) juveniles are likely to be consumed, particularly during the catfish’s active nocturnal periods. Adult Cherry Shrimp may coexist with smaller S. nigriventris specimens, but there is always a risk. Larger shrimp species such as Amano Shrimp (Caridina multidentata) are generally safe with this catfish due to their size. If you wish to maintain a thriving shrimp colony alongside these catfish, provide dense plantings and ample hiding spots for the shrimp, and accept that some predation of small or juvenile shrimp may occur.

Is the Upside-Down Catfish nocturnal?

Synodontis nigriventris is primarily crepuscular and nocturnal, meaning it is most active during dawn, dusk, and nighttime hours. However, aquarium-adapted specimens frequently become active during the day as well, particularly around feeding times and in tanks with subdued lighting, ample cover, and a comfortable group size. Floating plants, driftwood overhangs, and dim lighting all encourage daytime activity. Many experienced keepers report that their Upside-Down Catfish are visible and active throughout the day once they have settled into a well-designed tank.

How can I tell the difference between Synodontis nigriventris and other upside-down catfish species?

Several Synodontis species are sold under the common name “Upside-Down Catfish,” which can cause confusion. Synodontis nigriventris is the smallest and most commonly available of these, typically reaching only 7 to 10 cm. It is distinguished by its relatively small size, blotched brown patterning, and the pronounced reversed countershading (dark belly, lighter back). Synodontis contracta is another true upside-down swimming species but is less frequently encountered in the trade. Larger species such as Synodontis eupterus (Featherfin Squeaker) or Synodontis multipunctatus (Cuckoo Catfish) may occasionally swim inverted but do not do so as their primary swimming posture, and they grow significantly larger. Always check the scientific name when purchasing to ensure you are getting the correct species.

Bristlenose Pleco – Another popular catfish species ideal for community tanks, offering an