Rio Tocantins Angelfish (Pterophyllum scalare)

Rio Tocantins Angelfish at a glance

The Rio Tocantins Angelfish is a freshwater angelfish, Pterophyllum scalare, sold under the Rio Tocantins trade name. It is a South American cichlid with a tall, flattened body, long trailing fins and a calm, deliberate way of moving. FishBase calls it one of the most popular of all tropical aquarium fish.

Each purchase is one live fish of the size you choose. Two decisions matter more than anything else before you buy. First, the aquarium must be tall: an adult reaches about 15 cm in length but stands roughly 20–25 cm from fin tip to fin tip. Second, angelfish are social cichlids that should live as a compatible pair or in a planned group, never as a lone fish by default.

About the name

The accepted scientific name is Pterophyllum scalare (Schultze, 1823), in the cichlid family Cichlidae. Treat Rio Tocantins as a trade name rather than a separate species, and not as a guarantee of wild origin or of an exact collecting site. The Altum angelfish, Pterophyllum altum, is a distinct species; the silver, marble, koi, gold, black and platinum angelfish sold as P. scalare are colour or finnage forms of this one.

Is it the right fish for your aquarium?

What to expect as it grows

Young angelfish are small and short-finned when they arrive. As they mature they grow tall, pairs begin to form, and a pair may claim part of the tank, especially once it starts to breed. Planning for that adult stage from the beginning, with height, cover and a second option for surplus fish, is what makes angelfish straightforward rather than stressful.

Choosing a size and what arrives

There are five dispatch sizes: 3–4 cm, 4–5 cm, 5–6 cm, 6–7 cm and 7–9 cm. The size you select is the size supplied, not the adult size. Even a 7–9 cm fish is only around half its eventual length, and well short of its adult height, so size the aquarium for the adult. The product page shows which sizes can be ordered when you buy.

Because angelfish are best kept in pairs or groups, plan how many you need before choosing a size. If you are starting a group, buying the juveniles together at a similar size lets them grow up and pair off in the same tank.

Sex is guaranteed only when the selected option explicitly states male or female. This Rio Tocantins Angelfish listing has no sex-guaranteed option. Juveniles show no reliable outward difference between the sexes.

Gallery images have been digitally enhanced to improve image quality. Natural colour, pattern, size and maturity can vary between live animals. The gallery shows a fully finned fish; the juvenile you receive will be smaller and shorter-finned than the fish pictured.

If you are comparing forms, the angelfish collection includes other colour varieties of the same species. Our freshwater angelfish care guide goes further into water, tank height, social planning and health if you want the full picture before buying.

Planning the aquarium: height first

Height is the first measurement to check. Seriously Fish describes a tall tank of at least 50 cm as the recommendation for adult fish, with an aquarium of 100 × 40 × 50 cm, around 200 litres, as the smallest to consider. FishBase gives 100 cm as the minimum aquarium length. Our own planning point for an adult pair is the same: roughly 200 litres on a 100 × 40 cm base with about 50 cm of usable height, and more space for a group.

How the numbers fit together

The OATA care sheet for American cichlids gives these figures as general guidance for the group. Its 40-litre allowance is a useful cross-check: a pair of adult angelfish accounts for 80 litres of stocking before any other fish are added, which is why a community with angelfish quickly outgrows a 120-litre tank. A larger aquarium also keeps temperature and water quality more stable.

Why height matters so much

An angelfish grows upwards as well as forwards. A shallow tank that looks fine for a shop juvenile leaves an adult with too little room to turn without dragging its fins, and its long dorsal, anal and ventral fins are easily damaged. Measure the usable water depth, above the substrate and below the surface, rather than the glass height on the box.

Natural habitat and aquarium layout

FishBase records the species across the Amazon River basin in Peru, Colombia and Brazil, along the Ucayali, Solimões and Amazon rivers, and in rivers of Amapá in Brazil, the Oyapock in French Guiana and the Essequibo in Guyana. Eschmeyer's Catalog of Fishes gives the lower Amazon in Brazil as the type locality. The species is listed as Least Concern by the IUCN.

In the wild, FishBase records adults in swamps and flooded ground where aquatic and riverside vegetation is dense and the water is either clear or silty, noting that their colour is deeper in clear water. That points towards a planted, sheltered layout with vertical structure, rather than a bare show tank.

• Tall plants: Seriously Fish recommends a well-planted tank with tall leafy plants such as Amazon swords.
• Vertical wood: upright branches and roots echo the vegetated flooded ground of the wild habitat and give fish natural boundaries and cover.
• Open water: keep a clear central space where adults can turn with their fins fully spread.
• Substrate: fine gravel or sand; the OATA sheet notes that many American cichlids dig or sift the substrate when feeding or breeding.
• Safe décor: secure rocks and wood so digging cannot topple them, and avoid sharp edges near long fins.
• Lid: keep a secure lid, and cover any hazardous intakes.

Breaking up the space

Plants and wood placed to break sight lines give a subordinate fish somewhere to retreat and reduce uninterrupted lines of chasing. Broad leaves and upright surfaces also matter for breeding, because angelfish lay their eggs on vertical surfaces such as slate, broad-leaved plants or even the aquarium glass.

A note on plants: the OATA sheet warns that American cichlids as a group may dig up or eat live plants, but angelfish are among the calmer species, and Seriously Fish describes them as fish for a well-planted aquarium. Robust, well-rooted plants such as Amazon swords are the practical choice.

Water conditions

Stable water matters more than hitting one perfect number. These routine targets are where the FishBase species ranges and the broad OATA guidance for American cichlids overlap.

How the ranges compare

• FishBase lists 24–30 °C, pH 6.0–8.0 and 5–13 dH for the species as a whole.
• Seriously Fish gives 24–30 °C, pH 6.0–7.4 and 0–15 dGH, leaning towards slightly acidic to neutral water.
• The OATA sheet gives 22–27 °C, pH 6.5–8.0 and 4–12 °dH as a general guide for American cichlids, not a species optimum.

Both FishBase and Seriously Fish extend to 30 °C, but the routine target stops at 27 °C so the aquarium stays inside every source, including the OATA range. If your water is near neutral with moderate hardness, it already sits comfortably within all three. If your tap water is harder or more alkaline, steady conditions inside the routine range are far better than repeated attempts to push the pH down. Measure GH, KH and pH before changing your water source, and make any deliberate change gradually.

Test, then compare

Before adding fish, confirm with a test that ammonia and nitrite are at zero. A calendar alone cannot prove that a tank has cycled. Check the temperature with a thermometer rather than trusting the heater dial. If you are new to readings such as GH and KH, our water chemistry guide explains each one, and you can enter your measured results in the water parameter matcher to see how your water compares with these targets.

Filtration, flow and weekly care

Angelfish prefer gentle water movement, but gentle never means stagnant. Choose filtration that keeps the water clean and well oxygenated without forcing the fish to hold position against a hard current. For a tank of about 200 litres, Seriously Fish's rule of thumb is a filter rated at 800–1,000 litres per hour, a turnover of four to five times the volume an hour, and roughly 200–275 W of heating to hold 24–30 °C in a room at around 20 °C. Spread the outflow or aim it along the glass so the open swimming area stays calm.

A filter is essential in every aquarium. The RSPCA advice on aquarium filters explains why: fish release ammonia, which is toxic, and a working biological filter lets beneficial bacteria convert it into nitrite, also toxic, and then into the much safer nitrate. The OATA sheet adds that American cichlids can be stressed by even the smallest amounts of ammonia.

A weekly routine

• Change 25% of the water at least once every week, siphoning solid waste from the substrate.
• Test at least once a week so ammonia and nitrite never build up, and adjust the routine to what the results show.
• Treat all new water with tap water conditioner to remove chlorine or chloramine.
• Check the filter for blockages. Never clean the media under the tap; rinse it lightly in the tank water removed during the change, so the bacteria survive.

Stocking in stages

Filter bacteria need time to catch up each time fish are added and feeding increases. Stocking too many fish too quickly can cause new tank syndrome, where ammonia and nitrite climb and fish become ill and die. Add fish gradually, and if this is your first aquarium, our guide to setting up a first tropical tank covers maturing the tank before any livestock arrives.

Feeding angelfish well

Seriously Fish describes the angelfish as omnivorous, but wild fish feed mainly on zoobenthos: bottom-living small crustaceans and other aquatic invertebrates. The OATA sheet makes the same point for American cichlids generally, noting that they often prefer meaty foods.

Building the diet

• Staple: a nutritionally complete cichlid pellet, granule or flake, in a size the fish can swallow easily. Aquarium angelfish accept pellets and flakes.
• Variety: frozen or freeze-dried daphnia, brine shrimp and bloodworm, which the OATA sheet lists for smaller American cichlids.
• Treats stay treats: angelfish relish live and frozen foods, but bloodworm or brine shrimp on their own do not make a complete diet.

Food quality genuinely matters. A controlled feeding study on angelfish found that the type of feed affected both growth and reproductive performance, so a good staple is worth paying for.

How much and how often

The OATA sheet recommends feeding American cichlids only what they can eat within a few minutes, once a day. They can eat large amounts in one sitting, so it is easy to overfeed, and excess food and faeces break down into toxic waste. Angelfish are deliberate rather than fast feeders, so watch that every fish, including a shy or subordinate one, actually gets its share. Remove anything left uneaten.

Watch body shape over time as well. A fish that stays thin while the others fill out is often being kept away from food, which is a social problem rather than a diet problem.

Arrival and settling in

Every order is hand-packed by our team: fish are bagged in pure oxygen and packed in an insulated poly box, with a heat pack when the weather calls for it, then carried by a tracked, licensed live-animal courier. We email the tracking number and your confirmed delivery date, and the full details are on our delivery and Live Arrival Guarantee page.

Before it arrives

• The aquarium is fully cycled, with tests showing zero ammonia and nitrite.
• The temperature has been steady within 24–27 °C for several days.
• Tall plants and wood are already in place, so the new fish has cover from the start.
• Tank mates, if any, are settled, and there is a plan for where the angelfish group will live as adults.

On the day

1. Make sure someone is at the delivery address to receive the parcel, because live fish cannot be left unattended.
2. Before the parcel is opened, start one continuous unboxing video showing the sealed outer box, the opening, and the fish still inside the sealed bag.
3. Float the sealed bag in the aquarium for 20–30 minutes, acclimatising the fish slowly before releasing it.
4. Release the fish into the aquarium without pouring the bag water into your tank.
5. If anything has gone wrong, contact us the same day with your order number and the unboxing video. WhatsApp is the fastest route, and we will arrange a replacement or refund.

The Live Arrival Guarantee needs someone at the address to receive the parcel, the parcel opened and inspected on the day it arrives, and a continuous unboxing video that starts with the parcel still sealed.

Settling in

Healthy, settled angelfish swim steadily, breathe at a regular rate, hold their fins open and feed consistently. Over the first weeks, watch feeding time closely so every new fish gets food, and note which fish start to claim space. Early chasing between young angelfish is common as they sort themselves out; persistent exclusion of one fish from food or cover is the sign that something needs to change.

Health checks and what to do

Learn what normal looks like for your fish, then watch for changes. The OATA sheet lists the signs worth tracking in any aquarium fish:

• Swimming: hanging at the surface, sitting on the bottom or erratic movement.
• Colour: darker or paler than usual.
• Temperament: a change in aggression, or much more hiding.
• Breathing: gill covers moving faster or slower than normal.
• Appearance: white spots, fluffy growths, or damaged fins and scales.
• Condition and feeding: weight change, or less interest in food.

When something changes

1. Test ammonia, nitrite, nitrate, temperature and pH straight away. Treat any detectable ammonia or nitrite as urgent.
2. Compare the results with the conditions the fish normally lives in, and avoid sudden swings in pH, hardness or temperature while you investigate.
3. Isolate an affected fish only if a separate, mature aquarium is ready; a raw hospital tank can add stress.
4. Photograph the signs, note when they started, and get advice from a specialist aquatic retailer or a fish vet.
5. In the UK, use only a lawful treatment labelled for the species and system, following its instructions or a vet's direction.

Signs such as clamped fins, gasping, flashing, white spots or wounds are warnings, not a diagnosis, and there is no safe one-size recipe such as simply turning the heater up. The RSPCA fish health advice sets out the same water-quality-first approach. New fish added later should go through a mature quarantine set-up with separate equipment before joining the main tank.

If a fish jumps

Return it to suitable aquarium water immediately, using wet hands or a wet, soft net, and keep handling to a minimum. Watch its breathing, balance and any visible injury, check the lid, and seek fish-vet advice if recovery is not normal.

Sexing, pairing and breeding

Telling males from females

Angelfish are quite difficult to sex. According to Seriously Fish, males have smaller, pointed genital papillae, but these can usually only be seen when the fish are spawning. Behaviour can be a better clue, as males tend to be more aggressive and territorial when in breeding condition. Head shape, fin angle and temperament are not reliable ways to sex a juvenile.

How pairs form and breed

If you hope to breed, Seriously Fish suggests starting with a group of six juveniles and letting a pair form. A pair cleans a vertical surface, such as slate, a broad leaf or the aquarium glass, and lays adhesive eggs on it. Angelfish make good parents: both guard the eggs and then the young. Well-fed adults are less likely to eat their fry, although it does happen.

Two points are worth planning for. Pairs can change partners over time; behavioural research supports serial monogamy rather than a lifelong bond. And breeding sharply increases territorial defence, so a spawning pair in a crowded community can make life difficult for everyone else. A separate, mature aquarium for a breeding pair is the calmer long-term plan.

Pairs, groups and social needs

Angelfish are social. The OATA sheet says they should be kept in groups or as a pair at minimum, because a fish kept singly may become stressed. FishBase notes that aquarium fish are kept in groups of five or more, with pairs kept separately for breeding. Seriously Fish describes a generally peaceful cichlid that may squabble with its own kind, and so recommends small groups.

Choosing between a pair and a group

No single number suits every tank. Watch feeding access, fin condition, hiding and chasing, and treat a fish that is persistently excluded from food or cover as a welfare problem. Having a second suitable aquarium, or a realistic rehoming route, before trouble starts makes that decision far easier.

Choosing tank mates

Angelfish can live in a community, but they are still cichlids, and some aggression should be expected from time to time. The OATA sheet suggests calmer species such as angelfish can be mixed in a robust community aquarium with larger shoaling species, and that the more aggressive American cichlids must be kept alone or only with equally aggressive cichlids.

Questions to ask about every companion

Kinds that often work

• Larger, robust shoaling fish that are too big to swallow, in a tank big enough for both.
• Corydoras and bristlenose plecos are often considered because they use other levels of the tank, but species, adult size, floor space and water needs still decide the outcome.

Kinds to leave out

• Very small tetras, shrimp and fry, which remain at risk of being eaten.
• Persistent fin-nippers.
• Highly aggressive cichlids.

Adding angelfish to an established community

Look at the fish already in the tank as they will be in a year, not as they are today. Small tetras that live happily beside juvenile angelfish can become food once the angelfish are grown, and a resident fin-nipper that ignores other fish may go straight for long angelfish fins. The same applies in reverse: adding very small fish to a tank with adult angelfish is rarely a good idea. Increase stocking gradually so the filter keeps pace, and watch the first few feeds closely.

Mixing angelfish colour forms

Silver, marble, koi, gold and other colour forms sold as Pterophyllum scalare are the same species as this one, with the same care needs. In one tank they behave as one social group: they squabble, pair and defend territory with each other, so count them together when you plan space and group size. The Altum angelfish is a different species and should be researched separately rather than assumed to mix in the same way.

Rio Tocantins Angelfish questions

How big does a Rio Tocantins Angelfish get?

Plan for about 15 cm from snout to tail and roughly 20–25 cm from the tip of the dorsal fin to the tip of the anal fin. The height is what catches people out, because a juvenile that looks small in the bag grows upwards as well as forwards.

What size aquarium does Pterophyllum scalare need?

For an adult pair, plan on an aquarium with a base of about 100 × 40 cm and at least 50 cm of height, around 200 litres. OATA gives 120 litres as a general floor for a pair of smaller American cichlids and asks for 40 litres per adult angelfish when stocking, so a group or a mixed community needs more room than that.

How many angelfish should I keep together?

Do not keep one on its own: angelfish are social, and a fish kept singly may become stressed. Choose a compatible pair, or a group of juveniles in a larger aquarium so pairs can form naturally. FishBase suggests groups of five or more, and Seriously Fish suggests starting with six juveniles if you hope to breed. Have a plan for the extra fish once a pair claims territory.

Is the Rio Tocantins Angelfish good for beginners?

It suits a prepared beginner rather than a first-week one. It needs a fully cycled, tall aquarium, regular water tests, a pair or group, and companions chosen for their adult size and behaviour. Get the tank right first and it is a rewarding, long-term fish.

What does Pterophyllum scalare eat?

It is an omnivore that prefers meaty foods; wild fish feed mainly on small crustaceans and other aquatic invertebrates. Use a complete cichlid pellet, granule or flake as the staple and add frozen or freeze-dried daphnia, brine shrimp and bloodworm for variety. The OATA sheet advises feeding only what is eaten within a few minutes, once a day.

What temperature and pH does it need?

Aim for 24–27 °C, pH 6.5–8.0 and about 5–12 dGH, and keep conditions stable. Those routine targets are where the FishBase species ranges and the broad OATA guidance for American cichlids overlap; near-neutral water of moderate hardness sits comfortably inside them.

Is it aggressive, and does it nip fins?

Rio Tocantins Angelfish are generally peaceful for cichlids, but they can squabble with their own kind and become territorial when pairing or breeding. They may eat small fish. The bigger fin risk runs the other way: their own long fins are easily damaged by persistent fin-nippers, so keep those out of the tank.

Which fish can live with it?

OATA suggests calmer cichlids such as angelfish can share a robust community with larger shoaling species. Corydoras and bristlenose plecos are often considered because they use different levels of the tank, but check their adult size and water needs. Avoid very small tetras, shrimp and fry, persistent fin-nippers and highly aggressive cichlids.

How does the Rio Tocantins Angelfish arrive alive in the UK?

It is hand-bagged in pure oxygen, packed in an insulated poly box with a heat pack when the weather calls for it, and carried by a licensed live-animal courier, so someone must be in to receive it. Before opening, start a continuous unboxing video showing the sealed parcel, the opening and the fish still in the sealed bag; this is needed for any Live Arrival Guarantee claim. Then float the bag for 20–30 minutes before releasing the fish, without adding the bag water to your tank.

Sources

• FishBase species summary for Pterophyllum scalare: accepted name, family, native range, wild habitat, recorded water values and adult length.
• Eschmeyer's Catalog of Fishes: current accepted name, authorship, family placement, type locality and distribution.
• Seriously Fish species profile: aquarium size and height, planting, water, diet, behaviour, sexing and breeding.
• OATA care sheet: how to look after American cichlids: UK trade-body guidance for American cichlids as a group, covering water, tank size, stocking, maintenance, feeding and compatibility.
• RSPCA aquarium environment advice: filtration and the nitrogen cycle.
• RSPCA fish health and welfare: visible health signs and a water-quality-first response.
• Kasiri, Farahi and Sudagar (2012), feed types in freshwater angelfish: a controlled study of feed type, growth and reproduction in angelfish.
• Tropical Fish Co freshwater angelfish care guide and delivery page: our planning figures, routine water targets, packing and arrival steps.