Hockeystick Pencilfish

Quick summary

The Hockeystick Pencilfish (Nannostomus eques) is a peaceful, slender characin that swims at a distinctive head-up angle and thrives in soft, acidic water alongside other gentle species. It is well suited to planted community tanks and blackwater setups, though its small mouth and shy disposition mean it does best when kept with similarly calm tank mates and offered appropriately sized foods.

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Last researched and fact-checked: June 2025.

• 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 and health
• Frequently asked questions
• Related guides

Introduction

The Hockeystick Pencilfish, Nannostomus eques, is one of the most recognisable members of the pencilfish family thanks to two features that set it apart from its relatives. First, a bold black lateral stripe runs the full length of the body and bends sharply downward into the lower lobe of the caudal fin, forming the hockey stick shape that gives the species its common name. Second, and even more striking in life, is the fish’s habitual posture: it swims with its head angled markedly upward, typically at roughly 30 to 45 degrees from horizontal. This oblique swimming position is entirely normal for the species and should not be mistaken for a sign of illness or swim bladder problems. It is more pronounced in N. eques than in most other pencilfish and is one of the quickest ways to identify them in a dealer’s tank.

The species was first described by Steindachner in 1876 and belongs to the family Lebiasinidae, a group of small characiformes found across tropical South America. It has been kept in the aquarium hobby for well over a century, making it one of the longer-established pencilfish in the trade, and it remains readily available from specialist importers, though it is less commonly stocked than some of the more colourful Nannostomus species such as N. beckfordi or N. marginatus.

In the wild, Hockeystick Pencilfish inhabit slow-moving, often tannin-stained waters in the Amazon and Orinoco river basins. They tend to occupy the upper water column among floating plants and marginal vegetation, where their upward-tilted posture may help them feed on tiny invertebrates at the surface. This ecology translates well into the home aquarium, provided the keeper offers soft, acidic water, subdued lighting, and peaceful company.

For UK hobbyists, N. eques is a rewarding choice for anyone drawn to understated elegance rather than vivid colour. Their behaviour is fascinating to watch, especially in a group, and they are long-lived for their size when conditions are right. They do, however, demand attention to water chemistry and can be outcompeted at feeding time by bolder species, so they are best suited to an aquarist with at least a little experience.

Appearance

At first glance, the Hockeystick Pencilfish can appear rather plain compared to some of its more vividly marked Nannostomus relatives, but closer inspection reveals subtle beauty and a genuinely distinctive body plan. The body is slender and elongated, typical of the pencilfish group, reaching roughly 5 cm in total length when fully grown. The base colour is a warm golden-brown to olive on the dorsal surface, fading to a paler, sometimes silvery or cream tone on the belly.

The defining feature is the broad, dark brown to black lateral stripe. This stripe begins at the tip of the snout, passes through the eye, and continues in an unbroken line along the full length of the flank. At the caudal peduncle it angles sharply downward, extending into the lower lobe of the tail fin. This bend creates the hockey stick silhouette from which the species takes its most widely used common name. Above the main stripe, a thinner golden or coppery highlight line is often visible, adding a warm glow to the fish when viewed under appropriate lighting.

The fins are largely transparent to faintly yellowish, with the anal fin sometimes showing a small area of red or orange pigment, particularly in males. The dorsal fin is set well back on the body, roughly above the anal fin, which is a characteristic shared with other pencilfish. Males tend to be slightly slimmer and may show marginally more intense colouration, especially in the anal fin region, while females are a touch deeper-bodied when viewed from above, particularly when carrying eggs. However, sexing can be challenging outside of breeding condition.

Like all Nannostomus species, N. eques displays a markedly different colour pattern at night. The bold lateral stripe breaks up or fades substantially, and a series of darker blotches or oblique bars appear on the body. This nocturnal patterning can alarm keepers who are seeing it for the first time, but it is entirely normal. The daytime markings return within minutes of the lights coming on.

The most immediately striking visual feature, however, is the oblique swimming posture. At rest, feeding, or cruising through the water, N. eques holds its body at a pronounced head-up angle that is steeper than in most other pencilfish. This gives the fish a rocket-like appearance, which accounts for another of its common names. Groups hovering among floating plants at this angle create a very distinctive and appealing display.

Natural habitat

The Hockeystick Pencilfish is found across a broad range within the Amazon and Orinoco river basins, with records from Brazil, Colombia, Guyana, and Peru. Within these basins it is associated with slow-moving or still waters rather than fast-flowing main channels. Typical habitats include forest streams, flooded forest margins (igapó and várzea), oxbow lakes, and swampy backwaters where water flow is minimal and fallen leaves, submerged branches, and root tangles provide cover and foraging opportunities.

The water in these habitats is typically soft and acidic, often stained dark brown by tannins leached from decaying leaf litter and wood. pH values in the wild can be very low, frequently falling below 5.0 and sometimes approaching 4.0 in blackwater environments. General hardness is negligible. Temperatures remain warm and stable year-round, generally in the range of 24 – 28 °C (75 – 82 °F).

In the wild, N. eques tends to occupy the upper portion of the water column, often hovering among floating vegetation, surface roots, and overhanging marginal plants. This position, combined with their upward-angled posture, likely facilitates surface feeding on tiny invertebrates, insect larvae, and microorganisms that gather at or near the water’s surface. Dense surface cover also provides protection from aerial predators. They are typically found in loose groups, though they are not tightly schooling in the way that many tetras are.

The substrates in their natural habitats are usually composed of fine sand, mud, or thick layers of decomposed leaf litter. Light levels beneath the forest canopy and the dark water itself mean that illumination is low and diffuse. Replicating these conditions in the aquarium, even partially, brings out the best behaviour and colouration in captive fish.

Tank size and setup

A tank of at least 60 litres (approximately 13 UK gallons) is recommended for a group of Hockeystick Pencilfish. Because the species occupies the upper water column and does not need a great deal of horizontal swimming space, a tank with a generous surface area is more important than extreme length. A standard 60 cm aquarium works well as a starting point for a dedicated species tank or a small community built around similarly gentle fish. For a larger mixed community, a tank of 80 litres or more provides better scope for compatible tank mates.

The setup should reflect the species’ natural habitat as closely as practical. A dark, fine-grained substrate of sand or aquatic soil provides a good base and helps show the fish’s colouration to best effect. Driftwood, bogwood, and dried leaf litter (Indian almond leaves, oak leaves, or beech leaves) serve the dual purpose of providing visual cover and releasing tannins that soften and acidify the water. These additions are not strictly essential if water chemistry is managed by other means, but they are highly beneficial and create a more naturalistic environment.

Planting should include species that tolerate soft, acidic conditions. Floating plants are arguably the most important element, as N. eques naturally inhabits the area just beneath the surface and uses floating cover for security. Amazon frogbit (Limnobium laevigatum), dwarf water lettuce (Pistia stratiotes), salvinia, and red root floaters (Phyllanthus fluitans) all work well. Below the surface, undemanding species such as Java fern (Microsorum pteropus), Java moss (Taxiphyllum barbieri), Cryptocoryne species, and Anubias species complement the setup without requiring intense lighting.

Lighting should be subdued. The fish are more confident, display better colour, and exhibit more natural behaviour under dim conditions, which also suits the floating plants that form a key part of the setup. If brighter lighting is needed for other plants in the tank, a dense layer of floating vegetation will diffuse the light reaching the mid and upper water column where the pencilfish spend their time.

A secure, tight-fitting lid or cover glass is advisable. Although Hockeystick Pencilfish are not prolific jumpers, pencilfish in general can and do leap, particularly when startled or during water changes. A small gap is all it takes for a fish this size to escape.

Water parameters

Maintaining appropriate water chemistry is one of the most important aspects of keeping N. eques successfully. These fish originate from very soft, acidic waters and, while they are somewhat adaptable, they do best and are healthiest when these conditions are at least approximated in the aquarium.

A few points deserve emphasis. First, the species is genuinely sensitive to elevated nitrate levels and deteriorating water quality. Keeping nitrate below 10 ppm through regular partial water changes is a sound target, and consistently high levels will increase susceptibility to disease and reduce lifespan. Second, much of the UK mains water supply is moderately hard and alkaline, which is far from ideal for this species. Hobbyists in hard water areas will likely need to use RO (reverse osmosis) water, remineralised with an appropriate product to achieve the desired softness, or to mix RO water with tap water to bring hardness and pH into range. Third, stability matters as much as hitting a particular number. Sudden swings in pH or hardness are more dangerous than a reading that is slightly outside the ideal range but held steady.

Water changes of 15 – 25% weekly are a good routine. When using RO water, prepare the replacement water in advance and match the temperature closely before adding it to the tank. Indian almond leaves and alder cones in the tank will naturally buffer pH downward and release beneficial tannins, complementing the use of RO water.

Filtration and equipment

Filtration for a Hockeystick Pencilfish tank should prioritise biological efficiency and gentle flow. In the wild, N. eques lives in near-still water and will become stressed or unable to maintain its characteristic posture if subjected to strong currents. A sponge filter powered by an air pump is an excellent choice for a dedicated species tank or a small community. Sponge filters provide superb biological filtration, create very little water movement, and are safe for any fry that may appear. For larger setups, a small internal filter or a hang-on-back filter with an adjustable flow rate works well, provided the outflow is baffled or directed along the back glass to minimise current in the main swimming area.

External canister filters can also be used, but the spray bar or outlet should be positioned to avoid creating a strong current across the surface or mid-water zones. Lily pipe outlets set low in the tank, or a flow-reducing attachment, can help. Bear in mind that the fish primarily occupy the upper third of the water column, so flow in that zone is more disruptive to them than flow lower down.

A reliable heater is essential, as the species requires consistently warm temperatures. An adjustable heater rated appropriately for the tank volume, positioned near the filter outflow to ensure even heat distribution, is the standard approach. Use a separate thermometer to verify the heater’s accuracy, as built-in thermostats can drift over time.

Lighting, as noted in the tank setup section, should be kept subdued. A basic LED unit on a timer, providing 8 – 10 hours of moderate light per day, is sufficient when combined with floating plants. Avoid intense lighting or long photoperiods, which tend to make the fish nervous and can promote excessive algae growth in low-flow setups.

An air pump with a small airstone can be useful for maintaining adequate oxygenation without creating strong surface agitation, particularly in warmer tanks where dissolved oxygen levels are naturally lower. However, excessive surface disturbance is undesirable for a species that spends much of its time right at the surface.

Diet and feeding

In the wild, the Hockeystick Pencilfish feeds on tiny invertebrates, zooplankton, insect larvae, and other minute food items found at or near the water surface. In the aquarium, it accepts a range of foods, but its small mouth and shy feeding behaviour mean that some thought must go into what is offered and how.

The cornerstone of the diet should be high-quality micro-sized dried foods. Slow-sinking micro granules and crushed flake food are both accepted, though the fish will also readily take food from the surface, consistent with their head-up posture. Choose products from reputable manufacturers and vary the brand or formulation occasionally to provide a broader nutritional profile.

Live and frozen foods are extremely beneficial and should form a regular part of the feeding routine. Baby brine shrimp (newly hatched Artemia nauplii), micro worms, grindal worms, daphnia, and cyclops are all excellent choices and will be eagerly taken. These foods promote condition, enhance colour, and can be important in bringing fish into breeding readiness. Frozen foods should be thawed in a small amount of tank water and dispensed carefully to avoid overfeeding.

Feed small amounts two to three times per day rather than a single large feed. This suits the species’ natural grazing habit and helps ensure that all fish in the group get their share, as bolder individuals may otherwise monopolise a single feeding event. Because N. eques tends to feed in the upper water column, surface-dwelling or very slow-sinking foods are more accessible to them than items that drop quickly to the substrate. If kept with bottom-dwelling species, take care that enough food reaches the lower levels for those fish without overloading the tank.

Watch carefully during feeding to ensure every fish is eating. In a community setting, more assertive species can easily outcompete pencilfish. If this becomes a problem, target-feeding with a pipette or turkey baster near the pencilfish group, or feeding at the opposite end of the tank from boisterous species, can help.

Behaviour and temperament

The Hockeystick Pencilfish is a peaceful, somewhat reserved species that rarely causes problems in a community setting. It is not aggressive toward other fish and does not nip fins. Its defining behavioural trait is the head-up resting and swimming posture, which is more pronounced in this species than in any other commonly kept pencilfish. Fish will hover at an angle of roughly 30 to 45 degrees from horizontal, often clustered loosely among floating plant roots or beneath overhanging vegetation. This posture is completely normal and healthy. New keepers sometimes worry that their fish are ill, but as long as the fish are otherwise active, feeding, and displaying good colour, the angled posture is simply part of the species’ character.

N. eques is a social species and should be kept in a group. A minimum of six is often cited, but eight to ten or more is strongly recommended. In larger groups the fish are more confident, spend less time hiding, and display more interesting social interactions. Males may establish small territories and occasionally posture at one another, flaring their fins and intensifying their colour, but these encounters are mild and do not result in injury. Keeping a larger group diffuses any low-level tension and prevents any single individual from being targeted.

The species is predominantly active during daylight hours, spending much of its time in the upper third of the water column. It is not a fast swimmer and tends to drift and hover rather than dart. When startled, however, it can move quickly and may leap, which is why a tight-fitting lid is important. At night, fish settle lower in the water column and adopt their nocturnal colour pattern, becoming less active.

Compared to many small characins, Hockeystick Pencilfish are not particularly bold. They can be slow to settle into a new tank and may hide for the first few days after introduction. Providing plenty of floating plant cover, keeping the lighting subdued, and ensuring they are housed with gentle tank mates will help them acclimatise more quickly. Once settled, they become a constant, engaging presence in the upper water layers.

Tank mates

The Hockeystick Pencilfish is a gentle, small species that should only be housed with tank mates of a similarly peaceful disposition. Larger, boisterous, or aggressive fish will stress pencilfish, outcompete them for food, and potentially prey on them. The best companions are other soft-water species of comparable size and temperament, occupying different levels of the water column where possible, to reduce competition for space and food.

Good tank mates

• Ember tetra, a tiny, peaceful tetra that shares a preference for soft, acidic water and subdued lighting.
• Cardinal tetra, a classic soft-water community fish that occupies the mid-water zone and adds vivid colour.
• Green neon tetra, a small, undemanding tetra well suited to blackwater and planted setups.
• Pygmy corydoras, a diminutive bottom-dweller that is completely non-threatening and thrives in similar conditions.
• Otocinclus, a small algae-eating catfish that stays out of the pencilfish’s way and appreciates soft water.
• Chocolate gourami, a quiet, soft-water labyrinth fish that complements pencilfish well in a blackwater community.
• Beckford’s pencilfish, a close relative that occupies a similar niche and can coexist peacefully.
• Sparkling gourami, a small, peaceful gourami that inhabits the upper to mid-water and tolerates acidic conditions.
• Kuhli loach, a gentle, nocturnal bottom-dweller that makes a good clean-up companion in soft-water tanks.
• Dwarf pencilfish, another small Nannostomus species that cohabits well in a spacious, well-planted tank.

Fish to avoid

• Tiger barb, a known fin-nipper and boisterous swimmer that will harass and outcompete pencilfish at every opportunity.
• Convict cichlid, an aggressive, territorial cichlid far too large and belligerent for any pencilfish community.
• Angelfish, large enough to eat adult pencilfish and territorial, especially when breeding.
• Buenos Aires tetra, a large, active tetra that is too boisterous and will outcompete pencilfish for food.
• Chinese algae eater, a species that becomes aggressive and territorial with age and may harass small fish.
• Red-tail black shark, a highly territorial bottom-to-mid-water species that will chase and stress pencilfish.
• Flowerhorn cichlid, an extremely aggressive, large cichlid entirely incompatible with any small community fish.
• Betta, while sometimes recommended, bettas can be unpredictable and may target the pencilfish, which also occupy the upper water column.
• Jewel cichlid, an aggressive African cichlid that requires very different water chemistry and temperament.
• Common plecostomus, grows far too large for the tanks suited to pencilfish and produces heavy waste that degrades water quality.

Breeding

Breeding the Hockeystick Pencilfish in captivity is achievable but considered difficult. Like other Nannostomus species, N. eques is an egg-scattering species that provides no parental care and will readily consume its own eggs and fry if given the opportunity. Successfully raising a brood requires careful preparation, a separate breeding setup, and prompt removal of the adults or eggs after spawning.

Conditioning should begin several weeks before a breeding attempt. Select the healthiest, best-coloured adults and separate them by sex if possible. Feed a varied diet rich in live and frozen foods such as baby brine shrimp, daphnia, and micro worms. Females in good condition will appear noticeably plumper when viewed from above.

The breeding tank should be small (10 – 20 litres is sufficient) and set up with very soft, acidic water. A pH of 5.0 – 6.0 and a GH below 4 dGH is generally recommended. The temperature should be at the upper end of the species’ range, around 27 – 28 °C (81 – 82 °F). Filtration should be minimal, ideally a mature air-driven sponge filter providing gentle circulation. The tank should be dimly lit or shaded.

Spawning media such as fine-leaved plants (Java moss is commonly used), spawning mops, or a mesh grid on the tank bottom can be provided to catch the eggs and reduce predation. The eggs are small and semi-adhesive. Spawning typically occurs in the morning and may be preceded by the male displaying to the female with intensified colour and fin flaring. The female scatters small numbers of eggs among plants or in open water, and the male fertilises them.

After spawning, the adults should be removed immediately to prevent egg predation. The eggs are sensitive to light and fungus, so keeping the breeding tank dark and adding a few drops of methylene blue as a mild antifungal is a common practice. Hatching usually occurs within 24 – 36 hours at the recommended temperature, and the fry become free-swimming after a further two to three days once the yolk sac is absorbed.

The fry are extremely small and require infusoria, paramecium, or other microscopic first foods for the first week or so before graduating to freshly hatched baby brine shrimp nauplii. Growth is slow, and the fry are delicate in the early stages, requiring stable water parameters and very clean conditions. Small, frequent water changes with matched water are important during the rearing period.

While captive breeding of N. eques has been reported by dedicated hobbyists and breeders, it is not routine, and most fish available in the UK trade are wild-caught. Patience, attention to water chemistry, and a willingness to experiment with conditions are key to success.

Common diseases and health

The Hockeystick Pencilfish is not especially disease-prone when maintained in appropriate water conditions, but it is more sensitive to poor water quality and inappropriate chemistry than many commonly kept community fish. The most frequent health problems arise from elevated nitrate levels, excessively hard or alkaline water, or sudden changes in parameters. Under these stresses, the immune system becomes compromised and fish become vulnerable to opportunistic infections.

Ich (white spot disease) is probably the most commonly encountered ailment, manifesting as small white cysts on the fins and body. It typically appears following temperature fluctuations or the introduction of new, unquarantined fish. Treatment with a proprietary ich remedy at the manufacturer’s recommended dose, combined with a slight elevation in temperature to around 28 – 30 °C (82 – 86 °F), is usually effective. However, pencilfish can be sensitive to some medications, particularly those containing copper or formalin at high concentrations, so it is worth using half-doses initially and monitoring the fish closely. Bacterial infections, including fin rot and skin ulcers, can develop in tanks with chronically poor water quality. These are best prevented through consistent maintenance and, if they do occur, treated with appropriate antibacterial remedies alongside an improvement in water conditions.

Internal parasites can be a concern with wild-caught specimens, which make up the majority of N. eques in the UK trade. Fish that appear healthy but fail to gain weight or that produce pale, stringy faeces may be carrying intestinal parasites. Quarantining new arrivals for two to four weeks in a separate tank before adding them to the main display is strongly recommended, both to observe for signs of disease and to treat prophylactically if necessary. Maintaining excellent water quality, providing a varied and nutritious diet, keeping the fish in a suitably sized group to reduce stress, and avoiding incompatible tank mates are the most effective long-term health strategies for this species.

Frequently asked questions

Why does my Hockeystick Pencilfish swim at an angle?

This is completely normal. Nannostomus eques naturally swims with its head tilted upward at roughly 30 to 45 degrees. This oblique posture is a defining characteristic of the species and is not a sign of illness, stress, or swim bladder problems. Every healthy specimen will adopt this position.

How many Hockeystick Pencilfish should I keep together?

A minimum of six is commonly recommended, but a group of eight to ten or more is far better. In larger groups the fish are more confident, display more natural behaviour, and any minor male-to-male sparring is spread across several individuals rather than concentrated on one or two.

Can I keep Hockeystick Pencilfish in hard water?

They are not well suited to hard, alkaline water. While they may survive for a time, long-term health and any chance of breeding depend on soft, acidic conditions. UK hobbyists in hard water areas should plan to use RO water remineralised to the appropriate level, or a mix of RO and tap water, to achieve a GH of 1 – 8 dGH and a pH below 7.0.

Why do my pencilfish change colour at night?

All Nannostomus species display a different colour pattern in the dark. The bold lateral stripe fades or breaks up, and darker blotches or bars appear on the body. This is a normal nocturnal response. The daytime markings return within a few minutes of the lights coming on.

Are Hockeystick Pencilfish easy to breed?

No. Breeding is considered difficult. The species scatters eggs and provides no parental care, and the adults will eat eggs and fry if not separated. Very soft, acidic water and meticulous rearing of the tiny fry are required. Most fish in the trade are wild-caught rather than captive-bred.

What do Hockeystick Pencilfish eat?

They accept micro-sized dried foods such as crushed flake and small granules, but their diet should be

Related guides

• Golden Pencilfish
• Three-lined Pencilfish
• One-lined Pencilfish
• Cardinal Tetra
• Ember Tetra
• Marbled Hatchetfish