Costae Tetra Care Guide – Tank Setup, Feeding and Breeding

Quick summary

The Costae Tetra is an easy, hardy, and peaceful shoaling fish that’s great for beginners, provided you can keep a group of at least six in an 80 litre or larger planted tank with stable water quality. It’s an unfussy eater and tolerates a moderate range of parameters, making it a low-maintenance yet rewarding addition to a community aquarium.

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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 Costae Tetra (Moenkhausia costae) is a lesser-known yet thoroughly rewarding South American characin that deserves far more attention from the freshwater aquarium hobby than it currently receives. Belonging to the large and diverse genus Moenkhausia, this species offers a subtle but attractive appearance, peaceful temperament, and relatively undemanding care requirements that make it an excellent choice for community aquariums. While it may lack the instant visual punch of some of its more famous relatives such as the Diamond Tetra or the Red Eye Tetra, the Costae Tetra possesses an understated elegance that grows on the keeper over time, particularly when maintained in a well-planted aquarium with appropriate lighting.

First described by Eigenmann in 1907, Moenkhausia costae hails from river systems in eastern and north-eastern Brazil, where it inhabits a variety of freshwater environments ranging from clear streams to tannin-stained tributaries. Its relative obscurity in the aquarium trade means that hobbyists who do manage to acquire specimens are often pleasantly surprised by how well this species adapts to captive conditions. The Costae Tetra is a shoaling species that displays its best colouration and most natural behaviour when kept in groups, making it an ideal candidate for those who enjoy observing the social dynamics of a tightly knit school of fish.

This comprehensive care guide covers everything you need to know about keeping the Costae Tetra successfully in a home aquarium. From tank setup and water parameters to diet, breeding, and disease prevention, the information presented here will help both beginners and experienced aquarists provide optimal conditions for this charming little tetra.

Quick Stats

Scientific name	Moenkhausia costae
Common names	Costae Tetra, Costa’s Tetra
Family	Characidae
Origin	Eastern and north-eastern Brazil (Sao Francisco, Paraguacu, Jequitinhonha, and Itapicuru river basins)
Adult size	5-7 cm
Lifespan	3-5 years
Difficulty	Easy
Breeding difficulty	Moderate
Temperature	22-28 °C
pH range	6.0-7.5
General hardness (GH)	2-15 dGH
Carbonate hardness (KH)	2-10 dKH
Minimum tank size	80 litres
Conservation status	Least Concern

Appearance

The Costae Tetra possesses a moderately deep, laterally compressed body shape that is typical of many Moenkhausia species. Adults generally reach between 5 and 7 centimetres in total length, making them a mid-sized tetra that holds its own visually in a community aquarium without overwhelming smaller tank mates. The body has an overall silvery base colour that can range from pale silver to a slightly golden or olive-tinted hue depending on the fish’s condition, diet, and the ambient lighting in the aquarium.

One of the most distinguishing features of Moenkhausia costae is the prominent dark lateral stripe that runs from behind the gill cover to the base of the caudal fin, where it typically expands into a noticeable dark blotch on the caudal peduncle. This stripe can appear more or less pronounced depending on the fish’s mood and environmental conditions. Above this lateral band, a faint iridescent sheen can often be observed, particularly under side lighting, giving the fish a subtle but attractive shimmer as it moves through the water column.

The fins of the Costae Tetra are generally translucent to slightly yellowish, with the caudal fin sometimes displaying a faint dusky edge. The dorsal fin is relatively tall and triangular, while the anal fin is moderately elongated, a feature common among Moenkhausia species. The eyes are relatively large and can appear silvery or slightly reddish, adding a touch of brightness to the fish’s overall appearance. Like many characins, the Costae Tetra possesses an adipose fin – a small, fleshy fin situated between the dorsal and caudal fins.

Sexual dimorphism in the Costae Tetra is relatively subtle. Mature females tend to be slightly deeper-bodied and rounder in the belly region, particularly when carrying eggs. Males are often marginally slimmer and may display slightly more intense colouration, though these differences can be difficult to discern without careful observation. When in peak condition and provided with a varied diet rich in carotenoids, both sexes can develop enhanced colouration that makes them considerably more attractive than newly imported or stressed specimens might suggest.

Natural Habitat

Moenkhausia costae is native to several river systems in eastern and north-eastern Brazil, with its primary range encompassing the Sao Francisco River basin, the Paraguacu River basin, the Jequitinhonha River basin, and the Itapicuru River basin, among other smaller drainages in the region. This relatively wide distribution across multiple river systems speaks to the species’ adaptability, a trait that translates well into captive care.

In its natural environment, the Costae Tetra inhabits a variety of freshwater habitats including streams, rivers, and their associated tributaries. These environments can range from clear, moderately flowing waters with sandy or rocky substrates to slower-moving stretches with accumulated leaf litter and submerged vegetation. In some parts of its range, the species is found in waters that are mildly tannin-stained from decomposing organic matter, which creates slightly acidic, tea-coloured conditions.

The riparian zones along these waterways typically feature dense tropical and semi-arid vegetation, depending on the specific region. Overhanging trees and shrubs provide shade and contribute fallen leaves, branches, and fruit to the aquatic environment, creating a complex habitat with plenty of shelter and food sources. The substrate in these habitats is often composed of sand, fine gravel, and scattered rocks, with patches of submerged roots and aquatic plants providing additional structure.

Water conditions in these natural habitats vary seasonally, with temperature fluctuations occurring between the dry and wet seasons. During the wet season, water levels rise significantly, and the fish may move into newly flooded marginal areas to feed and breed. This seasonal variation is an important consideration for aquarists attempting to breed the species, as simulating these changes can sometimes trigger spawning behaviour. The water in these Brazilian river systems is generally soft to moderately hard, with a slightly acidic to neutral pH, though conditions can vary considerably depending on the specific locality and time of year.

The Costae Tetra shares its natural habitat with a wide array of other fish species, including various other tetras, small cichlids, catfish, and characins. Understanding this ecological context helps aquarists create more naturalistic setups and select appropriate tank mates that reflect the species’ natural community.

Tank Size and Setup

The minimum recommended tank size for a group of Costae Tetras is 80 litres, though a larger aquarium of 120 litres or more is preferable, particularly if you intend to keep them as part of a mixed community. As a shoaling species, the Costae Tetra should always be kept in groups of at least six individuals, with eight to twelve being ideal. Larger groups not only produce more natural behaviour but also result in a more visually impressive display as the fish move together through the aquarium.

When designing the tank layout, aim to replicate elements of the species’ natural habitat. A sandy or fine gravel substrate works well and provides a natural-looking base for the aquascape. Rounded river stones and smooth pebbles can be scattered across the substrate to add visual interest and mimic the rocky stretches of Brazilian waterways. Pieces of driftwood, particularly branching types, serve multiple purposes: they provide shelter, create natural-looking boundaries within the aquarium, and gradually release tannins into the water, which can benefit the fish by slightly softening and acidifying the water.

Live plants are highly recommended for a Costae Tetra aquarium. Dense plantings along the sides and back of the tank provide security and help the fish feel at ease, while an open swimming area in the centre or front of the tank allows the shoal to move freely. Suitable plant species include Vallisneria, Echinodorus (Amazon Swords), Cryptocoryne species, and floating plants such as Amazon Frogbit or Water Lettuce. Floating plants are particularly beneficial as they diffuse overhead lighting and create dappled shade patterns that closely resemble the fish’s natural environment.

Dried Indian Almond leaves (Terminalia catappa) or oak leaves can be added to the aquarium to further replicate the leaf-litter zones found in the species’ natural habitat. These leaves gradually decompose, releasing tannins and humic acids that tint the water a light amber colour, lower the pH slightly, and provide surfaces for beneficial biofilm growth. Microfauna that colonise decomposing leaves also serve as a supplementary food source for the fish.

A secure, well-fitting lid is advisable, as tetras can be surprisingly good jumpers, particularly when startled or during active periods. Ensure the tank has adequate lighting to support plant growth, but avoid excessively bright illumination unless it is tempered by floating plants or other shading elements. The Costae Tetra tends to display its best colouration under moderate, subdued lighting conditions rather than under intense overhead lights.

Water Parameters

Maintaining stable, appropriate water parameters is essential for the long-term health and vitality of the Costae Tetra. While this species is reasonably adaptable and can tolerate a moderate range of conditions, consistent water quality should always be prioritised over achieving any specific target number. Regular water changes of 20-30% per week are recommended to keep nitrate levels low and maintain overall water quality.

Temperature	22-28 °C
pH	6.0-7.5
General hardness (GH)	2-15 dGH
Carbonate hardness (KH)	2-10 dKH
Ammonia	0 ppm
Nitrite	0 ppm
Nitrate	Below 20 ppm

The ideal temperature range for the Costae Tetra is between 24 and 26 °C for general maintenance, though the species can comfortably tolerate temperatures from 22 to 28 °C. Avoid rapid temperature fluctuations, as these can stress the fish and make them susceptible to disease. A reliable aquarium heater with a thermostat is essential for maintaining consistent temperatures, particularly in cooler climates or in rooms where ambient temperature varies significantly.

Ammonia and nitrite must always be maintained at 0 ppm, as any detectable levels of these compounds are toxic to fish. Nitrate levels should be kept below 20 ppm through regular water changes and adequate biological filtration. If your tap water contains chlorine or chloramine, always use an appropriate water conditioner when performing water changes.

The Costae Tetra generally thrives in slightly acidic to neutral water, with a pH range of 6.0 to 7.5. In terms of hardness, soft to moderately hard water is preferred, though the species demonstrates reasonable flexibility in this regard. If you are keeping the fish purely for display purposes, matching your local water supply’s parameters (provided they fall within the acceptable range) is often the most practical approach. For breeding purposes, softer and more acidic conditions are typically more conducive to spawning success.

Filtration and Equipment

Effective filtration is the cornerstone of any successful aquarium, and the Costae Tetra’s tank is no exception. A filter that provides both mechanical and biological filtration, with a turnover rate of approximately four to six times the tank volume per hour, is ideal. For an 80-litre aquarium, this translates to a filter with a flow rate of roughly 320-480 litres per hour. However, the Costae Tetra does not appreciate excessively strong currents, so it is important to select a filter that allows flow adjustment or to use spray bars and outlet diffusers to moderate the water movement within the tank.

Hang-on-back filters, internal canister filters, and small external canister filters are all suitable choices for a Costae Tetra aquarium. External canister filters are often the preferred option for larger setups, as they offer superior biological filtration capacity, are quieter, and are located outside the tank, freeing up space within the aquarium. Sponge filters are another excellent option, particularly for breeding tanks, as they provide gentle filtration without creating currents strong enough to harm eggs or fry.

A reliable aquarium heater is essential for maintaining the consistent tropical temperatures that the Costae Tetra requires. Choose a heater with an appropriate wattage for your tank size – a general guideline is approximately 1 watt per litre of water. For added safety, consider using a heater with an integrated thermostat and an external thermometer to cross-check the temperature. In larger aquariums, using two smaller heaters rather than one large unit provides redundancy and more even heat distribution.

Lighting should be chosen to support any live plants in the aquarium while avoiding excessively intense illumination that could stress the fish. LED lighting systems with adjustable intensity and colour temperature are an excellent choice, allowing you to create a natural-looking light cycle and fine-tune the brightness to suit both the plants and the fish. A photoperiod of 8-10 hours per day is generally appropriate. If the aquarium does not include live plants, lower-intensity lighting is perfectly acceptable and may even encourage the fish to display more natural behaviour.

An air pump with an airstone can be a useful addition to provide supplementary oxygenation, particularly during warmer months when dissolved oxygen levels in the water naturally decrease. However, this is generally not essential if the filter provides adequate surface agitation. A gravel vacuum or siphon is an indispensable tool for performing water changes and removing detritus from the substrate during routine maintenance.

Diet and Feeding

The Costae Tetra is an omnivorous species with a broad and unfussy appetite, making feeding one of the more straightforward aspects of its care. In the wild, it feeds on a varied diet of small invertebrates, insect larvae, algae, plant matter, and organic detritus. Replicating this dietary diversity in captivity is key to maintaining optimal health, vibrant colouration, and strong immune function.

A high-quality flake food or micro-pellet formulated for tropical fish should form the staple of the Costae Tetra’s diet. Look for products with a balanced composition that includes both animal and plant-based ingredients, and avoid foods that list fillers or artificial additives as primary ingredients. The small mouth of this species means that food particles should be appropriately sized – crush larger flakes if necessary, and opt for micro-pellets rather than standard-sized granules.

To supplement the staple diet, offer a variety of live and frozen foods on a regular basis. Bloodworms, daphnia, brine shrimp (Artemia), mosquito larvae, and tubifex worms are all eagerly accepted and provide valuable protein and essential nutrients. Live foods in particular stimulate natural foraging behaviour and can help condition fish for breeding. Frozen foods are a convenient and widely available alternative that retains much of the nutritional value of live offerings.

Vegetable matter should not be overlooked in the Costae Tetra’s diet. Spirulina-based flakes or wafers, blanched vegetables such as spinach, courgette, or cucumber, and commercially available algae wafers can all be offered periodically. These plant-based foods provide fibre and essential vitamins that contribute to overall digestive health and well-being.

Feed the Costae Tetra two to three times daily, offering only as much food as the fish can consume within two to three minutes. Overfeeding is a common mistake in aquarium keeping and can lead to water quality issues, obesity, and associated health problems. Remove any uneaten food promptly to prevent it from decomposing and fouling the water. A regular fasting day once per week can be beneficial for the fish’s digestive system, though this is optional rather than essential.

Behaviour and Temperament

The Costae Tetra is a peaceful, sociable species that thrives in the company of its own kind. It is a classic shoaling fish, and when kept in appropriate numbers, the group will spend much of its time swimming together in loose formation, exploring the tank, and foraging for food. This shoaling behaviour is not merely aesthetic – it serves an important psychological function, providing the individual fish with a sense of security that reduces stress and encourages natural behaviour patterns.

When kept in groups that are too small (fewer than six individuals), Costae Tetras may become nervous, withdrawn, or even mildly nippy towards other fish. This is a stress response rather than an inherent character trait, and it is almost always resolved by increasing the group size. In an appropriately sized group, the species is remarkably well-behaved and is unlikely to bother any of its tank mates.

The Costae Tetra is primarily a midwater swimmer, occupying the middle and upper regions of the water column for most of the day. It is an active species that appreciates having open swimming space, though it will also venture into planted areas and around driftwood structures to explore and forage. The fish tends to be most active during daylight hours and may settle into quieter, less conspicuous positions as the lights dim in the evening.

Within the group, a subtle social hierarchy may establish itself, with occasional brief chases or displays between individuals, particularly among males. These interactions are normal and rarely result in any injury. Providing adequate space and visual barriers in the form of plants and decor helps to diffuse any minor territorial behaviour and ensures that all individuals can find refuge if needed.

Overall, the Costae Tetra’s temperament makes it an ideal candidate for peaceful community aquariums. Its calm disposition, attractive appearance, and engaging shoaling behaviour combine to make it a rewarding species to observe and keep.

Tank Mates

The Costae Tetra’s peaceful and sociable nature makes it compatible with a wide range of similarly tempered freshwater species. When selecting tank mates, focus on species that share comparable water parameter requirements and that are unlikely to view the Costae Tetra as prey or to compete aggressively for food and territory. Avoid pairing them with large, predatory, or highly aggressive species that could intimidate or harm them. The best community setups for the Costae Tetra feature a mix of peaceful tetras, small catfish, dwarf cichlids, and other gentle community fish.

Good tank mates

Cardinal Tetra – A similarly peaceful shoaling tetra that shares comparable water parameter preferences and occupies the same midwater region without conflict.
Rummy Nose Tetra – Another tight-shoaling South American tetra that coexists peacefully and creates a visually striking display alongside the Costae Tetra.
Ember Tetra – A small, docile tetra that adds warm colour to the aquarium and is far too peaceful to cause any issues.
Bronze Corydoras – A bottom-dwelling catfish that occupies a different area of the tank and helps clean up uneaten food from the substrate.
Bristlenose Pleco – A peaceful algae-eating catfish that stays out of the Costae Tetra’s way and contributes to tank maintenance.
Apistogramma cacatuoides – A dwarf cichlid that is generally peaceful towards midwater tetras and adds interesting behaviour to the community.
Harlequin Rasbora – A gentle, shoaling cyprinid that thrives in similar water conditions and cohabits harmoniously with tetras.
Kuhli Loach – A shy, bottom-dwelling loach that is completely non-aggressive and adds diversity to the lower levels of the aquarium.
Otocinclus – A small, peaceful algae-eating catfish that is an excellent community companion and helps control algae growth.

Fish to avoid

Oscar – A large, predatory cichlid that would readily consume Costae Tetras and requires vastly different tank conditions.
Red-bellied Piranha – An aggressive predator that would view small tetras as food and is entirely unsuitable as a tank mate.
Jaguar Cichlid – A highly aggressive and territorial cichlid that grows far too large and would pose a serious threat to small tetras.
Green Terror – An aggressive cichlid that becomes increasingly territorial as it matures and would harass or consume Costae Tetras.
Tiger Barb – A notorious fin nipper that could stress and damage the Costae Tetra, particularly if kept in insufficient numbers.
African Leaf Fish – A stealthy ambush predator that would readily prey upon small tetras in the aquarium.
Convict Cichlid – A pugnacious cichlid that becomes highly aggressive during breeding and would bully the peaceful Costae Tetra.
Bucktooth Tetra – Despite being a tetra, this species is a known scale-eater and should never be housed with smaller, peaceful fish.

Breeding

Breeding the Costae Tetra in captivity is achievable for hobbyists with some prior experience in breeding egg-scattering characins. While not as straightforward as some of the more commonly bred tetra species, success can be achieved with proper preparation, conditioning, and attention to environmental conditions.

To begin, select healthy, well-conditioned adults for the breeding project. Separate the sexes for one to two weeks prior to the breeding attempt and feed them generously with live and frozen foods such as bloodworms, daphnia, and brine shrimp. This conditioning period is important for building up the female’s egg reserves and stimulating both sexes’ reproductive readiness.

Set up a dedicated breeding tank of approximately 30-40 litres with soft, slightly acidic water (pH 6.0-6.5, GH 2-5 dGH) at a temperature of 26-27 °C. The tank should be dimly lit, as bright light can inhibit spawning and is harmful to the eggs. Use a sponge filter for gentle filtration without creating strong currents that could disturb the eggs. The bottom of the tank should be covered with a spawning grid, a layer of glass marbles, or dense clumps of fine-leaved plants such as Java Moss to protect the eggs from the parents, which will readily consume them if given the opportunity.

Introduce the conditioned pair (or a small group of two males and three females) to the breeding tank in the evening. Spawning typically occurs the following morning, often triggered by the first light of dawn. The female will scatter her eggs among the plants or over the substrate, and the male will fertilise them as they are released. A single spawning event can produce several hundred small, semi-adhesive eggs.

Remove the adults immediately after spawning is complete, as they will consume the eggs if left in the tank. The eggs are light-sensitive, so keep the breeding tank in subdued lighting or cover it partially with a towel. The eggs typically hatch within 24-36 hours, and the resulting fry will become free-swimming approximately three to four days after hatching, once they have absorbed their yolk sacs.

Feed the free-swimming fry with infusoria or commercially available liquid fry food for the first few days, gradually transitioning to freshly hatched brine shrimp nauplii and microworms as they grow. Maintain pristine water quality in the fry tank with frequent small water changes, taking care to match the temperature and chemistry of the replacement water. Growth is steady but not rapid, and the young fish can typically be transitioned to crushed flake food after several weeks.

Common Diseases

The Costae Tetra is a reasonably hardy species, but like all aquarium fish, it is susceptible to a range of common diseases, particularly when water quality is compromised or when the fish is stressed. Prevention through good husbandry practices – regular water changes, appropriate feeding, stable water parameters, and quarantining new additions – is always preferable to treatment.

Ich (white spot disease), caused by the protozoan parasite Ichthyophthirius multifiliis, is one of the most common ailments encountered in freshwater aquariums. It presents as small, white, salt-grain-like spots on the skin, fins, and gills of affected fish. Infected fish may also clamp their fins, become lethargic, and rub against hard surfaces in an attempt to dislodge the parasites. Treatment involves gradually raising the water temperature to 28-30 °C and administering a proprietary ich medication according to the manufacturer’s instructions. Early intervention is key to successful treatment.

Fin rot is a bacterial infection that causes progressive deterioration of the fins, which may appear ragged, frayed, or discoloured. It is almost always associated with poor water quality or physical damage to the fins. Treatment involves addressing the underlying water quality issues through water changes and, in more advanced cases, using an appropriate antibacterial medication. Maintaining clean water is both the best prevention and the most important component of treatment.

Fungal infections, often appearing as white, cotton-like growths on the skin or fins, can occur following physical injury or in tanks with poor water quality. Anti-fungal treatments are widely available and generally effective when used promptly. Again, ensuring optimal water conditions is essential both for treatment and prevention.

Internal parasites can occasionally affect the Costae Tetra, particularly in wild-caught specimens. Symptoms may include weight loss despite normal feeding, lethargy, abnormal faeces (white, stringy droppings), and a gradual decline in condition. Anti-parasitic medications formulated for internal parasites can be administered through medicated food or directly into the water. Quarantining new fish for two to four weeks before introducing them to the main aquarium is one of the most effective ways to prevent the introduction of parasites and other pathogens.

Neon tetra disease (Pleistophora hyphessobryconis), despite its name, can affect a wide range of tetra species. It is caused by a microsporidian parasite and manifests as loss of colour, cysts or lumps beneath the skin, difficulty swimming, and a wasting appearance. Unfortunately, there is no reliable treatment for this disease, and affected fish should be humanely euthanised and removed from the tank to prevent further spread. Purchasing fish from reputable sources and maintaining a strict quarantine protocol are the best preventative measures.

FAQs

How many Costae Tetras should I keep together?

The Costae Tetra is a shoaling species that should be kept in groups of at least six individuals, with eight to twelve being the ideal number. Larger groups feel more secure, display more natural behaviour, and are less likely to exhibit stress-related issues such as hiding or fin nipping. A group of ten or more swimming together in a well-planted aquarium creates a truly impressive and engaging display.

Are Costae Tetras suitable for beginners?

Yes, the Costae Tetra is generally considered suitable for beginners, provided the aquarium has been properly set up and cycled before the fish are introduced. Their tolerance of a moderate range of water parameters, peaceful temperament, and unfussy feeding habits make them a forgiving species for those new to the hobby. The key requirements are maintaining stable water quality, feeding a varied diet, and keeping them in an appropriately sized group.

Can Costae Tetras live with shrimp?

Adult Costae Tetras can generally coexist with larger shrimp species such as Amano Shrimp without significant issues. However, they may opportunistically prey on very small shrimp, particularly dwarf shrimp species like Cherry Shrimp, and will almost certainly eat shrimplets. If you wish to maintain a breeding colony of dwarf shrimp, it is advisable to provide plenty of dense plant cover and hiding spots, or to house the shrimp in a separate dedicated tank.

What is the best temperature for Costae Tetras?

The optimal temperature range for general maintenance of the Costae Tetra is 24-26 °C, though they can tolerate temperatures from 22 to 28 °C. Consistency is more important than hitting an exact number, so choose a temperature within the ideal range and maintain it steadily using a reliable aquarium heater. For breeding, slightly warmer temperatures of around 26-27 °C may help stimulate spawning behaviour.

Why are my Costae Tetras losing colour?

Colour loss in the Costae Tetra can be caused by several factors. Stress is the most common culprit, which may result from poor water quality, an inadequate group size, aggressive tank mates, insufficient hiding places, or excessively bright lighting. A monotonous diet lacking in variety can also lead to faded colouration over time. Address these potential causes systematically by testing your water parameters, ensuring the fish are kept in a sufficiently large group, reviewing the tank setup for stressors, and incorporating live or frozen foods and colour-enhancing foods into their diet. If colour loss is accompanied by other symptoms such as lethargy, clamped fins, or loss of appetite, disease should be investigated.

Diamond Tetra – A closely related Moenkhausia species with similar care requirements and a spectacular iridescent appearance.
Red Eye Tetra – Another popular Moenkhausia species that shares comparable tank and water parameter needs with the Costae Tetra.
Cardinal Tetra – One of the most popular South American tetras and an excellent community companion for the Costae Tetra.
Ember Tetra – A small, peaceful tetra ideal for nano and community setups that pairs well with other gentle species.
Bronze Corydoras – A hardy bottom-dwelling catfish that complements midwater tetras perfectly in a South American biotope setup.