Pterophyllum scalare red cap

Decide whether this angelfish fits your aquarium

The red cap freshwater angelfish (Pterophyllum scalare) is a tall-bodied freshwater cichlid from South America’s Amazon basin. It reaches 15 cm in total length and needs considerable vertical room for its extended fins. This colour form suits an intermediate keeper who can provide a mature, tall aquarium, stable warm water and a plan for social and territorial behaviour.

FishBase places Pterophyllum scalare in the cichlid family Cichlidae and records its distribution across the Amazon basin in Peru, Colombia and Brazil, with further localities in French Guiana and Guyana. Adults inhabit swamps and flooded ground where aquatic and riverside vegetation is dense and the water may be clear or silty. Eschmeyer’s Catalog of Fishes also recognises Pterophyllum scalare as the accepted name.

The red cap wording identifies the colour form offered here; its care should still be planned around the adult shape and behaviour of P. scalare. A small fish can look comfortable in a shallow juvenile setup while lacking the height, turning room and territory it will need as it grows.

Understand the fish and size choice

One purchase supplies one red cap freshwater angelfish in the size selected. Use the live size selector to choose from the labels shown there: 1 cm, 1.5-2 cm, 2.5-3 cm, 3 - 3,5 cm, 4 - 5 cm, 5 - 5,5 cm, L (5.5-6 cm), XL (6-7 cm) or XXL (>7.5 cm). The size you select is the size supplied, not the adult size.

Those labels describe dispatch size, so use them to judge the fish’s immediate feeding needs, companion size and safe introduction. They do not reduce the adult aquarium requirement. A smaller angelfish still needs a long-term plan for a 15 cm fish with tall extended fins, while a larger grade must have suitable adult-scale space ready before it arrives.

Sex is guaranteed only when the selected option explicitly states male or female. This Pterophyllum scalare red cap listing has no sex-guaranteed option. Do not use forehead shape, fin angle, colour, dispatch size or a gallery scene to choose a sex.

Some gallery images have been digitally enhanced to improve image quality. They show the listed type of animal rather than guaranteeing the exact markings of the individual supplied, so natural colour and pattern can vary. The scenes show the tall angelfish shape, and the body pattern and colour of the fish you receive can differ from them; one image showing two fish does not change the sold unit of one animal per purchase.

If you are comparing colour forms before settling on this one, browse our angelfish collection and apply the same adult-space, water and temperament checks to every choice.

Set the non-negotiable plan before purchase

Plan around roughly 200 litres, a 100 × 40 cm footprint and about 50 cm of usable height for an adult pair. A group or mixed community needs more room, broken sight lines and a practical way to separate or rehome a fish if territorial behaviour becomes persistent.

• Adult length: plan for 15 cm total length, while allowing extra vertical clearance for the extended dorsal and anal fins.
• Routine water: keep 24–27°C, pH 6.5–7.4 and 5–12 dGH, the overlap of FishBase, Seriously Fish and OATA guidance, with zero detectable ammonia and nitrite.
• Social plan: use a genuinely compatible pair or a deliberately managed group. FishBase advises groups of five or more, while OATA says angelfish should be kept in a group or, at minimum, a pair.
• Temperament: expect a generally peaceful cichlid that may squabble and become territorial, particularly during pair formation or breeding.
• Care level: intermediate, because adult height, social dynamics and companion screening require preparation rather than difficult water chemistry alone.

Read our complete freshwater angelfish care guide when planning the whole aquarium. The litres, dimensions, group structure and exit plan work together; no single number can compensate for poor dimensions or incompatible fish.

Plan the aquarium around adult height

Use roughly 200 litres with a base around 100 × 40 cm and about 50 cm of usable height as the adult-pair plan. Seriously Fish describes a 100 × 40 × 50 cm aquarium, approximately 200 litres, as the smallest that should be considered. Horizontal room still matters because an adult must turn, feed and move away from its companion without dragging long fins through decor.

OATA’s American-cichlid sheet gives at least 120 litres for a compatible pair of smaller species and says an adult angelfish aquarium must be sufficiently tall. That is broad group guidance rather than a promise that every nominal 120-litre tank has suitable dimensions. Tropical Fish Co therefore uses roughly 200 litres as the more useful adult-pair planning point.

Read size measurements correctly

Plan for 15 cm total length. Measure that 15 cm from snout to tail tip; the tall dorsal and anal fins add height on top of it. The Tropical Fish Co guide notes that extended fins can make an adult roughly 20–25 cm tall, so tank height cannot be inferred from body length alone.

A long but shallow aquarium fails the height test, while a tall narrow aquarium may fail the turning-room and territory tests. Measure the usable internal space rather than relying only on the manufacturer’s headline volume.

Hold stable water within the care overlap

Keep routine water at 24–27°C, pH 6.5–7.4 and 5–12 dGH. This range overlaps FishBase’s 24–30°C, pH 6.0–8.0 and 5–13 dGH values, Seriously Fish’s 24–30°C, pH 6.0–7.4 and 0–15 dGH aquarium range, and OATA’s 22–27°C, pH 6.5–8.0 and 4–12 dGH American-cichlid guidance.

Stability matters more than chasing a single ideal reading. Test the aquarium before choosing the fish, then compare the measured temperature, pH and hardness with the routine range. Use our water matcher to compare those readings without assuming that every value inside a broad range is equally suitable for an abrupt transfer.

Change chemistry only from measurements

If GH, KH and pH are unfamiliar, read the water chemistry guide before altering tap water. Do not copy a fixed mixture of tap and reverse-osmosis water from another aquarium. The resulting hardness, buffering and pH depend on the water being mixed, so test both the starting water and the prepared replacement water.

• Temperature: use a thermometer to check 24–27°C instead of relying only on the heater dial.
• pH: keep it within 6.5–7.4 and avoid abrupt elective adjustment.
• General hardness: maintain 5–12 dGH and measure before adding minerals or diluting tap water.
• Ammonia and nitrite: both should remain at zero detectable mg/l.
• Nitrate: keep it no more than 20 mg/l above your normal tap-water level, the limit OATA sets for American cichlids.

A sudden pH, hardness or temperature change can add stress even when the final number sits inside the target range. Make routine adjustments gradually. Detectable ammonia or nitrite is different: treat it as an urgent water-quality problem and act promptly to protect the fish.

Build biological filtration before adding fish

Add this angelfish only after testing confirms zero detectable ammonia and nitrite. A mature biological filter must process the waste produced by the fish and its food; elapsed time alone cannot show whether that capacity exists. If this is your first setup, follow our guide to preparing and maturing a tropical aquarium before livestock is introduced.

The RSPCA explains that a working biological filter supports bacteria that convert toxic ammonia into nitrite and then into safer nitrate. Test results reveal whether that process is coping with the aquarium’s actual waste load.

Choose flow that cleans without exhausting the fish

Seriously Fish uses a turnover of four to five times the aquarium volume per hour for its approximately 200-litre example, equivalent to a filter rated around 800–1000 litres per hour. Treat the rating as a starting point because media, pipework and maintenance can affect real flow. Angelfish prefer gentle movement, so distribute the return instead of forcing them to fight a concentrated current throughout the day.

• Before introduction: confirm zero ammonia and nitrite and a stable temperature.
• After adding fish: test often enough to catch a rise before behaviour deteriorates.
• At feeding time: remove uneaten food so it cannot decay into additional waste.
• At the filter: check for blockages, reduced output and uncovered hazardous intakes.
• When stocking: add fish gradually so the bacterial population can adjust to greater waste production.

Extra litres help buffer change, but volume does not replace filtration, testing or maintenance. Likewise, a powerful filter cannot make overcrowding safe if the aquarium lacks territory, height or oxygen exchange. Match the biological load, filter capacity and social plan rather than treating one piece of equipment as the whole solution.

Create height, cover and turning room

Arrange tall plants or upright wood around open turning space. FishBase records wild adults among dense aquatic and riverside vegetation in swamps and flooded ground, while Seriously Fish recommends a well-planted aquarium with tall leafy plants and gentle flow. Use that structure to provide cover and interrupt long lines of sight without filling every route through the tank.

Build the layout from the fish outward

• Vertical structure: place tall plants or wood where they create separate visual zones.
• Open water: leave a clear route wide enough for an adult to turn without catching its extended fins.
• Substrate: use fine aquarium gravel or sand, which OATA says the aquarium should have because many American cichlids dig or sift the substrate when feeding or breeding.
• Edges and gaps: avoid sharp surfaces and narrow traps around the dorsal, anal and trailing pelvic fins.
• Stability: secure wood, stones and planted decor so digging cannot undermine them.
• Cover: use a secure lid and check openings around cables and pipes.

For a pair, create more than one sheltered zone so either fish can move out of direct view. For a group, repeat those barriers across the aquarium rather than placing one dense clump at an end. A fish that is repeatedly chased needs a route to leave the aggressor’s sight, not merely a decorative cave that can become a dead end.

Watch how the fish use the layout. If one individual stays pinned behind equipment, cannot approach food or is chased whenever it enters open water, revise the barriers and use the separation plan. If every route is cramped, remove or reposition decor rather than adding more cover blindly. The aim is a tall, structured aquarium with genuine movement and choice, not a bare box or an impassable thicket.

Feed a complete staple with measured variety

Use a nutritionally complete cichlid pellet, granule or suitable flake as the staple, choosing a size the fish can swallow. Seriously Fish describes P. scalare as omnivorous and notes that wild fish feed predominantly on zoobenthos such as small crustaceans and other aquatic invertebrates. It also records acceptance of dried foods and enjoyment of live or frozen items in aquaria.

Add suitable frozen or freeze-dried foods for variety. OATA names daphnia, brine shrimp and bloodworm for smaller American cichlids, but these attractive foods should supplement rather than replace a complete staple. A controlled angelfish feeding study supports the importance of feed composition and variety without creating one fixed household menu.

Use one measured daily feeding routine

OATA advises feeding once a day and offering only what the fish can consume within a few minutes. Start conservatively, observe every fish eating and remove excess. Increase or reduce the amount from direct observation rather than assuming that a larger mouth or enthusiastic response means the fish needs an unrestricted portion.

Overfeeding creates uneaten food and excess waste, which can raise toxic nitrogen compounds. Underfeeding a subordinate fish can occur even when the group appears eager, so watch individuals rather than judging the aquarium by the fastest feeder. A consistent body profile, regular interest in food and clean water are more useful checkpoints than dramatic feeding behaviour.

Use tests to set the maintenance routine

Make a 25% partial water change at least once every week and test the water at least once a week, keeping a closer routine whenever readings, stocking or feeding call for it. OATA strongly recommends a 25% partial water change at least once every week for American cichlids, with testing at least once a week so ammonia and nitrite do not build up.

Complete the routine without damaging the filter

1. Test ammonia, nitrite, nitrate and temperature before interpreting a behaviour change.
2. Prepare replacement water with a conditioner that treats chlorine or chloramine.
3. Match routine replacement water closely enough to avoid an abrupt temperature or chemistry swing.
4. Siphon solid waste from accessible areas of gravel or sand during the partial change.
5. Check the filter for blockages and reduced output.
6. If filter media needs cleaning, rinse it lightly in water removed from the aquarium, never under the tap.

Keep a simple record of readings and maintenance. A sequence shows whether nitrate is climbing faster, the filter is losing output or a change followed increased feeding. Waiting for cloudy water or obvious distress allows a manageable trend to become a welfare problem.

Respond to health changes with water tests first

Look for steady swimming, regular breathing, clear eyes, open undamaged fins, intact scales, a consistent body profile and reliable feeding. Warning signs include gasping, erratic balance, sitting unusually at the surface or bottom, clamped fins, white spots, fluffy growths, wounds, sudden hiding or loss of appetite. The RSPCA’s fish-health guidance supports checking visible condition and water quality promptly.

If a change appears, test the water immediately and compare it with the fish’s established conditions. Treat detectable ammonia or nitrite as urgent. Move a fish only when the separate aquarium is mature and suitable, and seek specialist fish-vet advice for diagnosis or treatment. Do not use a temperature increase, fasting routine or medication recipe as a substitute for identifying the problem.

Follow the arrival procedure exactly

Start filming every delivery before the parcel is opened. Make one short, continuous unboxing video showing the parcel still sealed, the parcel being opened and the fish still inside the bag before anything is disturbed.

Arrange for someone to receive the parcel because live fish cannot be left unattended. Tropical Fish Co hand-bags fish in pure oxygen, uses an insulated poly box and adds a heat pack when the weather calls for it. A licensed live-animal courier carries the parcel, with tracking and the confirmed delivery details sent by email.

Float the bag for 20–30 minutes before releasing the fish, and never pour the bag water into the aquarium. These steps and the claim requirements are set out in the delivery and Live Arrival Guarantee policy.

Prepare the aquarium before the parcel arrives

Complete these aquarium checks before the fish is introduced:

• Confirm the aquarium is mature, filtered and large enough for the fish and its companions.
• Test for zero detectable ammonia and nitrite.
• Check that temperature, pH and hardness sit within the intended routine range.
• Complete disruptive layout work before introduction rather than while the fish is settling.
• Make sure visual barriers and a separation plan are ready where other angelfish or territorial fish are present.

OATA advises increasing aquarium populations slowly because the beneficial bacteria in a mature filter must adjust when waste and feeding rise. After introduction, observe swimming, breathing, fin position, colour, feeding access and interactions with every companion. A fish hiding briefly and a fish being persistently excluded require different responses, so look for a pattern rather than reacting to one moment.

If breathing changes, fins clamp, balance becomes unusual or appetite drops, test ammonia, nitrite, nitrate and temperature before guessing at a cause. If another fish blocks food or chases the newcomer repeatedly, use the prepared compatibility response rather than waiting for torn fins or weight loss.

Screen every companion before mixing species

Choose companions by adult size, fin behaviour, temperament, water overlap, feeding speed and territory. Angelfish can live in a robust community, but they remain cichlids and may defend a partner or spawning surface. Individual behaviour changes the outcome, so a stocking plan is conditional rather than a promise of harmony.

Know which fish to avoid

Avoid tiny prey-sized fish, including very small tetras, small shrimp and fry, as well as persistent fin-nippers, highly aggressive competitors and much faster-feeding species. Seriously Fish specifically warns that small fish such as tetras may be eaten, while the Tropical Fish Co guide extends that predation warning to very small tetras, small shrimp and fry. Small size at introduction is not protective because companions and angelfish change as they grow.

OATA identifies robust, larger shoaling fish as a possible community category for calmer American cichlids such as angelfish. That category still requires compatible water, enough swimming room and a feeding plan. Corydoras and bristlenose plecos are sometimes considered because they use different aquarium levels, but species, adult size, floor area and water requirements must still be checked.

Before mixing animals, write down the adult size and water range of each one, then identify where it feeds and which territory it uses. If any answer depends on a juvenile staying small or a territorial fish never breeding, change the plan before introduction.

Manage pairs, groups and territory actively

Keep a genuinely compatible pair or a deliberately planned group. FishBase advises five or more angelfish, Seriously Fish recommends small groups because individuals may squabble, and OATA says a pair or group should be the minimum because a singleton may become stressed. These positions describe different workable social plans rather than making two randomly selected fish a bonded pair.

Choose the plan you can support

A juvenile group can allow a pair to form, but social rank within the group then changes feeding and aggression. Breeding behaviour can also make a previously calm fish defend a vertical leaf, slate, glass panel or surrounding territory. Treat prolonged hiding, missed meals or torn fins as signs that the arrangement needs intervention.

Use feeding and movement as practical checks. Every individual should be able to cross the aquarium, leave another fish’s line of sight and obtain food. Persistent chasing, cornering or blocked feeding calls for the same response. Rearranging barriers may help when the layout is the problem, but separation or rehoming is the appropriate response when aggression continues.

For a worked example, an aquarium holding a compatible pair and robust larger shoaling fish still needs more than the pair’s basic footprint because the community shares swimming and feeding space. A group of five angelfish needs more than multiplying a nominal litre allowance: territory shape, visual barriers, filtration and an exit plan all affect whether weaker individuals can escape pressure.

Answer common buyer questions

How big does Pterophyllum scalare red cap get?

It reaches 15 cm in total length. Its extended dorsal and anal fins also require a tall aquarium, so plan around adult dimensions rather than the dispatch size.

What aquarium size does Pterophyllum scalare red cap need?

Plan roughly 200 litres with about a 100 × 40 cm footprint and 50 cm of usable height for an adult pair. A group or community needs more room, visual barriers and a separation plan.

How many Pterophyllum scalare red cap should I keep together?

Use a genuinely compatible pair or a deliberately planned group. FishBase advises five or more, while OATA says a pair or group is the minimum and warns that a singleton may become stressed.

Does this angelfish suit beginners?

Pterophyllum scalare red cap has an intermediate care level. It suits a prepared keeper with a mature, tall aquarium who can test water, screen companions and respond to territorial aggression.

What does Pterophyllum scalare red cap eat?

Feed a complete cichlid pellet, granule or suitable flake as the staple, with suitable frozen or freeze-dried variety. OATA advises one daily portion consumed within a few minutes.

What temperature and pH does it need?

Keep this fish at 24–27°C, pH 6.5–7.4 and 5–12 dGH. These routine values are the overlap of FishBase, Seriously Fish and OATA guidance.

Is this angelfish aggressive or likely to nip fins?

Treat it as semi-aggressive: it is generally peaceful but may squabble and become territorial during pair formation or breeding. Keep persistent fin-nippers away because they can damage its extended fins.

Which fish or invertebrates can it live with?

Robust larger shoaling fish with overlapping water needs may suit a carefully planned community. Avoid tiny prey-sized fish, including very small tetras, small shrimp and fry, as well as fin-nippers, highly aggressive competitors and much faster-feeding species.

How does this fish arrive alive in the UK?

Start filming every delivery before opening the parcel, making one short, continuous unboxing video that shows it still sealed, then being opened and the fish still in the bag. It is hand-bagged in pure oxygen and placed in an insulated poly box with a heat pack when weather calls for it. Someone must receive the parcel; float the bag for 20–30 minutes before release and never pour bag water into the aquarium.

Consult the care references

• FishBase: Pterophyllum scalare — identity, family, distribution, habitat, environmental values, length and aquarium notes.
• Seriously Fish: Pterophyllum scalare — aquarium dimensions, water, diet, behaviour and reproduction.
• OATA: How to look after American cichlids — UK group guidance for water, feeding, social care and maintenance.
• RSPCA: Aquarium environment and filtration — biological filtration and waste processing.
• RSPCA: Fish health and welfare — visible health signs and water-quality-first action.
• Eschmeyer’s Catalog of Fishes — accepted scientific identity and distribution.
• Kasiri, Farahi and Sudagar: angelfish feed study — controlled comparison of feed types.