Emerald Catfish Care Guide — Tank Setup, Feeding and Breeding

Introduction

The Emerald Catfish, known scientifically as Brochis splendens, is one of the most attractive bottom-dwelling catfish available to freshwater aquarists. Often mistaken for the more commonly kept bronze or green Corydoras species, the Emerald Catfish is a distinctly larger and more robustly built fish with a truly stunning iridescent green sheen that catches the light beautifully under aquarium conditions. Its metallic, jewel-like appearance has earned it a well-deserved place in community tanks around the world.

Originally described by Castelnau in 1855, this species hails from the slow-moving, densely vegetated waterways of South America. It has been a staple in the aquarium trade for decades, prized not only for its appearance but also for its peaceful disposition and relative hardiness. While it shares many behavioural traits with its Corydoras cousins — including a fondness for group living and a penchant for sifting through substrate — its larger adult size and deeper body profile set it apart as a more substantial presence in the aquarium. Some taxonomists have reclassified the genus Brochis into Corydoras, so you may encounter this species listed as Corydoras splendens in some references, though the name Brochis splendens remains widely used in the hobby.

This guide covers everything you need to know to keep Emerald Catfish successfully, from tank setup and water parameters to diet, breeding, and compatible tank mates. Whether you are a seasoned fishkeeper looking to add a splash of emerald to your community aquarium or a relative newcomer drawn in by this species’ charm, you will find all the practical information you need here.

Quick Stats

Scientific name	Brochis splendens (syn. Corydoras splendens)
Common names	Emerald Catfish, Emerald Brochis, Emerald Green Cory, Green Catfish, Common Brochis
Family	Callichthyidae
Origin	South America — Amazon basin, including Brazil, Peru, Ecuador, and Colombia
Adult size	7–9 cm (approximately 3–3.5 inches)
Lifespan	5–8 years in captivity
Difficulty	Easy
Breeding difficulty	Moderate
Temperature	22–28 °C
pH range	5.8–7.5
General hardness (GH)	2–15 dGH
Carbonate hardness (KH)	2–12 dKH
Minimum tank size	150 litres
Conservation status	Not Evaluated

Appearance

The Emerald Catfish is a stocky, deep-bodied member of the Callichthyidae family. It is noticeably larger and more heavily built than most Corydoras species, with a more pronounced forehead and a deeper body profile that gives it an almost helmeted look. The most immediately striking feature is its colouration: the flanks and dorsal surface are covered in overlapping bony scutes that reflect a vivid, metallic emerald green under aquarium lighting. Depending on the angle and intensity of light, this green can shift to include hints of blue or teal, creating a shimmering effect that is truly eye-catching.

The ventral surface is considerably paler, typically a creamy white or pinkish hue, providing a clean contrast against the rich green of the upper body. The fins are generally translucent with a slight yellowish or amber tint, and the dorsal fin is notably larger than that of most Corydoras species, containing more rays — a key distinguishing feature of the Brochis genus. Typically, the dorsal fin has between 10 and 17 soft rays, compared with the 7 or 8 rays commonly seen in Corydoras.

Like other members of its family, the Emerald Catfish possesses two pairs of short barbels on the upper and lower jaw, which it uses to probe the substrate in search of food. The eyes are relatively large and mobile, set high on the head, giving the fish an alert, inquisitive expression. Males and females can be difficult to distinguish when young, but adult females tend to be broader and rounder when viewed from above, particularly when laden with eggs. Males are generally slightly more slender and may appear marginally smaller at maturity.

Natural Habitat

In the wild, Brochis splendens is found throughout the upper Amazon basin, with populations recorded in Brazil, Peru, Ecuador, and Colombia. It inhabits slow-moving rivers, tributaries, floodplain lakes, and shallow, marshy areas where the water is warm, soft, and often stained with tannins from decaying organic matter. The substrate in these environments is typically composed of fine sand or mud, overlaid with a layer of decomposing leaf litter and plant debris.

Vegetation in these habitats tends to be dense, with floating plants shading the water surface and marginal plants lining the banks. The water is generally shallow and sluggish in flow, and dissolved oxygen levels can sometimes drop, which is why Emerald Catfish — like their Corydoras relatives — have the ability to gulp air from the surface and absorb oxygen through the intestinal lining. This adaptation allows them to survive in periodically hypoxic conditions, though in the aquarium it should not be relied upon as a substitute for proper aeration.

These catfish are social animals in the wild, typically found in sizeable shoals that forage together across the riverbed. Their natural diet consists of insect larvae, small worms, crustaceans, and organic detritus sifted from the substrate. Understanding these natural conditions is key to replicating a suitable environment in captivity — soft, slightly acidic water, a fine-grained substrate, plenty of cover, and the company of conspecifics all contribute to keeping this species healthy and displaying its best colours.

Tank Size and Setup

Given that Emerald Catfish are notably larger than most Corydoras species and are best kept in groups, a minimum tank size of 150 litres is recommended. This provides enough floor space for a group of six or more individuals to forage comfortably without feeling cramped. Larger tanks of 200 litres or above are preferable, especially if you intend to keep them as part of a mixed community, as additional volume improves water stability and gives these active fish room to exhibit natural behaviours.

Substrate choice is of critical importance for all callichthyid catfish. A fine, smooth sand substrate is ideal, as the Emerald Catfish spends a great deal of its time rooting through the substrate with its sensitive barbels. Coarse gravel, sharp-edged substrates, or substrates with rough textures can cause damage to the barbels and underside of the fish, leading to infections and erosion over time. Play sand, pool filter sand, or purpose-made aquarium sand in a natural colour all work well.

The aquarium should provide a mix of open foraging areas and sheltered retreats. Driftwood, smooth rocks, and dense plantings around the tank’s perimeter create a sense of security, while leaving the central and frontal areas relatively clear gives the fish space to move as a group. Live plants are highly recommended, as they replicate the species’ natural habitat and help maintain water quality. Hardy species such as Java fern, Anubias, Amazon swords, and Vallisneria are all excellent choices. Floating plants are a worthwhile addition, as they diffuse light and reduce the sometimes shy nature of these catfish.

Lighting need not be particularly intense; indeed, moderate to subdued lighting is closer to the conditions these fish experience in the wild and tends to bring out their best colour, as the metallic green sheen is most vivid when light hits the flanks at an angle rather than from a harsh overhead source. A dark substrate further enhances the visual impact of their iridescent scales.

Water Parameters

Emerald Catfish are reasonably adaptable when it comes to water chemistry, but they do best in conditions that approximate their natural Amazonian habitat. Maintaining stable parameters is more important than hitting an exact number, so focus on consistency and avoid sudden fluctuations.

Temperature	22–28 °C
pH	5.8–7.5
General hardness (GH)	2–15 dGH
Carbonate hardness (KH)	2–12 dKH
Ammonia	0 ppm
Nitrite	0 ppm
Nitrate	Below 20 ppm

A temperature around 24–26 °C is a comfortable middle ground for most community setups. While the species can tolerate the upper end of its temperature range, prolonged exposure to very warm water can reduce dissolved oxygen levels and shorten lifespan, so aim for the moderate range unless you are deliberately conditioning fish for breeding. The pH should ideally sit in the slightly acidic to neutral range, and soft to moderately hard water is preferred. Many aquarists find that the addition of Indian almond leaves or driftwood, which release tannins and gently lower pH, is appreciated by these fish and encourages more natural behaviour.

As with all aquarium fish, ammonia and nitrite must be maintained at zero at all times. Emerald Catfish are somewhat sensitive to elevated nitrate levels and poor water quality in general, so regular partial water changes of around 25–30% per week are essential. Clean, well-oxygenated water is particularly important; while these fish can take supplementary gulps of air from the surface, frequent surface breathing in an aquarium setting is often an indicator that dissolved oxygen levels or water quality need attention.

Filtration and Equipment

A reliable filtration system is essential for keeping Emerald Catfish in good health. These are mesophilic bottom dwellers that produce a moderate bioload, especially when kept in the recommended groups, so the filter should be rated for the full volume of the tank and ideally provide gentle to moderate flow. External canister filters are an excellent choice for tanks of 150 litres and above, offering high biological filtration capacity without creating excessively strong currents at the substrate level. Hang-on-back filters can work well for smaller setups, though a sponge pre-filter over the intake is advisable to prevent fine sand from being drawn in.

Internal sponge filters are another viable option, particularly in breeding tanks, as they provide biological filtration and gentle water movement without posing any risk to eggs or fry. Whichever system you choose, ensure the flow is not so powerful that it disturbs the substrate or creates strong currents across the bottom of the tank, as Emerald Catfish prefer calm, slow-moving water.

An aquarium heater with a reliable thermostat is necessary to maintain tropical temperatures. Choose a heater appropriate for your tank volume and consider using a heater guard to protect the fish, particularly if they tend to rest against it. A thermometer placed at the opposite end of the tank from the heater will help you verify temperature consistency. Aeration via an air stone or spray bar is beneficial, particularly in warmer weather or if the tank is densely stocked, as it helps maintain adequate dissolved oxygen levels near the substrate where these catfish spend most of their time.

A tight-fitting lid or cover glass is recommended, as Emerald Catfish will occasionally dash to the surface to gulp air, and in rare cases may leap if startled. The lid also helps reduce evaporation and maintains a warm, humid air layer above the water surface, which is important for the health of their supplementary air-breathing mechanism.

Diet and Feeding

Emerald Catfish are omnivores with a hearty appetite, and feeding them is generally straightforward. In the wild, they forage along the substrate for insect larvae, small crustaceans, worms, and organic debris, and in the aquarium they retain this industrious bottom-feeding behaviour. A varied diet is the key to keeping them in peak condition and displaying their most vibrant coloration.

A high-quality sinking pellet or wafer designed for bottom feeders should form the staple of their diet. These foods are formulated to sink quickly and hold their shape long enough for substrate-feeding fish to find and consume them. Supplement the staple diet regularly with frozen or live foods such as bloodworm, tubifex, daphnia, brine shrimp, and mosquito larvae. These protein-rich foods are not only relished but also play an important role in conditioning fish for breeding. Blanched vegetables such as courgette, cucumber, and shelled peas can be offered occasionally as a source of fibre and micronutrients.

Feed once or twice daily, offering only as much as the group can consume within a few minutes. It is worth feeding after lights out or during the evening, as Emerald Catfish tend to be most active during low-light periods and will forage more enthusiastically when the tank is dimmer. Be mindful that in a busy community tank, faster-swimming mid-water or surface-dwelling species may intercept food before it reaches the substrate. Using sinking foods that fall quickly and targeting specific areas of the tank with a pipette or feeding tube can help ensure the catfish receive their fair share.

Avoid relying solely on scraps and leftovers from other fish. While Emerald Catfish will certainly scavenge uneaten food, this is not a reliable or nutritionally complete feeding strategy. Targeted feeding ensures they receive the nutrients they need and reduces the risk of food decomposing on the substrate and degrading water quality.

Behaviour and Temperament

The Emerald Catfish is a thoroughly peaceful and sociable species that poses no threat to any other aquarium inhabitants. It is an obligate shoaling fish that should always be kept in groups of six or more; solitary individuals or pairs tend to be stressed, reclusive, and far less active than those kept in an appropriate group. In a well-sized shoal, these catfish are remarkably engaging to watch, moving across the substrate in loose formation as they probe the sand for morsels, occasionally dashing to the surface to gulp air before returning to their business below.

Their activity levels tend to peak during the early morning and evening hours, though a well-settled group in a dimly lit or well-planted tank will often be active throughout the day. They are not territorial in any meaningful sense and coexist peacefully with one another regardless of sex ratio. Mild jostling over a particularly appealing food item may occur, but this never escalates to genuine aggression.

One behaviour that sometimes causes concern among new keepers is the aforementioned surface breathing. It is perfectly normal for callichthyid catfish to make occasional trips to the surface to swallow a mouthful of air, which is then processed in the posterior intestine for supplementary oxygen absorption. However, if this behaviour becomes very frequent, it is worth checking dissolved oxygen levels, stocking density, and overall water quality, as excessive surface breathing may indicate a problem. In a well-maintained tank with adequate filtration and aeration, these trips should be infrequent and brief.

Emerald Catfish are generally hardy, but they can be sensitive to sudden changes in water chemistry or temperature. When introducing new specimens, a slow and thorough acclimatisation over at least 30–45 minutes is advisable. They can also be somewhat prone to stress when exposed to aggressive or highly boisterous tank mates, so care should be taken when selecting companions.

Tank Mates

The Emerald Catfish’s peaceful nature makes it compatible with a wide range of similarly tempered freshwater species. The ideal tank mates are calm, non-aggressive fish that occupy different areas of the water column, creating a harmonious community. Avoid pairing them with large, predatory, or highly territorial species that may bully, stress, or attempt to eat them.

Good tank mates

Cardinal Tetra — A classic Amazonian mid-water shoaling fish that shares similar water parameter preferences and poses no threat to bottom dwellers.
Rummy-Nose Tetra — Another peaceful South American tetra that thrives in soft, slightly acidic water and makes an excellent visual complement to Emerald Catfish.
Harlequin Rasbora — A gentle, easy-going shoaling fish that occupies the mid-water zone and coexists peacefully with bottom dwellers.
Pearl Gourami — A calm, elegant upper-to-mid-water species that is large enough to coexist without competition and shares a preference for well-planted tanks.
Bristlenose Pleco — A peaceful algae-eating catfish that occupies different feeding niches and rarely competes for the same food.
Kuhli Loach — A non-aggressive bottom dweller that is active at different times and cohabits well with callichthyid catfish.
Cherry Barb — A small, peaceful barb that stays in the middle of the water column and does not harass slower-moving bottom feeders.
Bronze Corydoras — A closely related species that shares identical care requirements and often shoals alongside Emerald Catfish.
Dwarf Gourami — A calm labyrinth fish that rarely ventures to the substrate and makes a colourful addition to an Emerald Catfish community.
Otocinclus — A tiny, peaceful algae grazer that presents no conflict with Emerald Catfish and benefits from similar water conditions.

Fish to avoid

Oscar — A large, predatory cichlid that will readily consume or injure smaller tank mates, including Emerald Catfish.
Jack Dempsey — A highly territorial and aggressive cichlid that would bully and stress peaceful bottom dwellers.
Red-Tail Catfish — A massive predatory catfish that would view Emerald Catfish as prey, entirely unsuitable as a companion.
Green Terror — An aggressive South American cichlid known for territorial behaviour that would make life miserable for peaceful catfish.
Tiger Barb — A notorious fin-nipper that can harass slower-moving species and cause chronic stress in calmer tank mates.
African Cichlids (Mbuna) — Require hard, alkaline water conditions incompatible with Emerald Catfish and are far too aggressive for a peaceful community.
Flowerhorn Cichlid — An extremely territorial and aggressive fish that should generally be kept alone, far too dangerous for Emerald Catfish.
Red-Bellied Piranha — A predatory species that poses an obvious lethal threat to any small or mid-sized tank mate.

Breeding

Breeding Emerald Catfish in the home aquarium is achievable but requires some preparation and patience. It is not as frequently accomplished as breeding common Corydoras species, largely because Brochis splendens can be somewhat more particular about conditioning and water conditions. However, with the right approach, success is certainly within the reach of a dedicated hobbyist.

Begin by establishing a well-conditioned group of at least six to eight adults in a spacious, well-maintained tank. Sexing can be challenging, but females tend to be rounder and broader when viewed from above, particularly when full of eggs, while males are slightly slimmer. A ratio of two males to each female is commonly recommended to encourage natural breeding behaviour.

Conditioning the group for spawning involves gradually increasing the proportion of high-protein live and frozen foods in their diet over a period of two to four weeks. Bloodworm, brine shrimp, and daphnia are all excellent conditioning foods. Simultaneously, simulate the onset of the rainy season by performing a large water change of around 50% using slightly cooler water — dropping the tank temperature by two to three degrees Celsius. This temperature drop, combined with a slight reduction in water hardness and an increase in oxygenation via an air stone, often triggers spawning behaviour within a day or two.

Spawning in Brochis splendens follows a pattern broadly similar to that seen in Corydoras. The female will clean a flat surface — typically the glass wall of the tank, broad plant leaves, or the underside of driftwood — and deposit small clusters of adhesive eggs. The classic T-position, where the female clasps the male’s pelvic fins with her own pectoral fins during fertilisation, is commonly observed. A single spawning event can produce between 300 and over 900 eggs, though numbers vary considerably depending on the size and condition of the female.

After spawning is complete, it is advisable to remove either the adults or the eggs to a separate rearing tank, as the parents may consume the eggs if left unattended. The eggs are relatively large, pale, and slightly amber in colour. At temperatures around 25–26 °C, they typically hatch within four to five days. The fry are initially sustained by their yolk sacs and will begin free-swimming a day or two after hatching. First foods should include infusoria, microworms, or commercially available liquid fry food, graduating to freshly hatched brine shrimp nauplii as the fry grow. Maintaining impeccable water quality in the rearing tank is critical during the early weeks, as the fry are highly susceptible to bacterial and fungal infections.

Common Diseases

Emerald Catfish are generally hardy when kept in appropriate conditions, but like all aquarium fish they are susceptible to certain health issues, particularly when water quality is neglected or they are subjected to stress.

White spot disease, or ich, caused by the parasite Ichthyophthirius multifiliis, is perhaps the most frequently encountered ailment. It manifests as small white granules scattered across the body and fins. Emerald Catfish, like other scaleless and armoured catfish, can be more sensitive to some ich medications — particularly those containing copper or malachite green at full concentration. When treating, it is advisable to use half the standard dose of medication or opt for a heat-based treatment, gradually raising the temperature to 30 °C over 48 hours while increasing aeration, and maintaining this for approximately ten days.

Barbel erosion is a common problem in callichthyid catfish kept on rough or dirty substrates. The barbels become shortened, reddened, and in severe cases may erode entirely, significantly impairing the fish’s ability to forage. Prevention is straightforward: maintain a fine, smooth sand substrate and keep it clean through regular vacuuming during water changes. If erosion is detected, improving substrate hygiene and water quality typically allows the barbels to regenerate over time.

Fin rot, characterised by the progressive fraying and disintegration of the fins, is usually a secondary infection resulting from poor water quality or physical damage. Improving water conditions and, if necessary, treating with a broad-spectrum antibacterial medication will resolve most cases. Fungal infections, presenting as white cottony growths on the body or fins, can occur following injuries or in tanks with suboptimal water conditions; antifungal treatments are effective when combined with water quality improvements.

Internal parasites can occasionally affect wild-caught specimens or those obtained from less reputable sources. Symptoms may include weight loss despite a good appetite, white or stringy faeces, and a general decline in condition. Antiparasitic foods or treatments containing praziquantel or levamisole can be effective. Quarantining new arrivals for two to four weeks in a separate tank before adding them to the main display is a sensible precaution that can prevent the introduction of parasites and other pathogens to an established community.

FAQs

How many Emerald Catfish should I keep together?

Emerald Catfish are obligate shoaling fish and should be kept in groups of at least six. Larger groups of eight to twelve or more are even better, as the fish feel more secure in greater numbers and will display more natural, active behaviour. Solitary individuals or very small groups tend to be stressed, reclusive, and more prone to health problems.

Are Emerald Catfish the same as Corydoras?

While they are very closely related and belong to the same family, Callichthyidae, the Emerald Catfish was traditionally placed in the separate genus Brochis, distinguished from Corydoras by its larger size, deeper body, and greater number of dorsal fin rays. Recent taxonomic revisions have moved Brochis into Corydoras, so you may see this fish listed as Corydoras splendens. In practical terms, their care requirements are very similar to those of larger Corydoras species, but they are distinctly bigger and more robust.

Why does my Emerald Catfish keep swimming to the surface?

Occasional trips to the surface to gulp air are entirely normal for callichthyid catfish. They possess a modified intestine that can absorb atmospheric oxygen, a useful adaptation in their native habitat where dissolved oxygen levels can drop. However, if your fish are making frequent and frantic dashes to the surface, this may indicate low dissolved oxygen, poor water quality, or overcrowding. Check your water parameters, ensure adequate aeration, and verify that the tank is not overstocked.

Can Emerald Catfish live with shrimp?

Emerald Catfish are generally safe with larger shrimp species such as Amano shrimp and adult Cherry shrimp. However, very small shrimp and shrimplets may occasionally be consumed, particularly if they are encountered during the catfish’s substrate-foraging activities. If you are breeding shrimp, it is best to provide dense plant cover or a separate breeding compartment to give the young shrimp a chance to grow to a safe size.

Do Emerald Catfish eat algae?

While Emerald Catfish may incidentally consume small amounts of algae as they sift through the substrate, they are not effective algae eaters and should not be kept for this purpose. Their diet in the wild and in captivity is primarily composed of meaty foods, organic detritus, and sinking prepared foods. If you need algae control, consider adding a dedicated algae-eating species such as Otocinclus or a Bristlenose Pleco alongside your Emerald Catfish.

Related Guides

Bronze Corydoras Care Guide — A closely related and highly popular species with similar care requirements, ideal for those comparing Corydoras options.
Panda Corydoras Care Guide — Another beloved member of the Corydoras genus that thrives in comparable community setups.
Bristlenose Pleco Care Guide — An excellent bottom-dwelling companion species that complements Emerald Catfish well in a community tank.
Kuhli Loach Care Guide — A peaceful substrate-dwelling species that shares similar habitat preferences and makes a compatible tank mate.
Amazon Biotope Tank Setup Guide — A comprehensive guide to creating an authentic South American biotope, ideal for showcasing Emerald Catfish in a natural setting.