Scalar common blue (Pterophyllum scalare)

Scalar common blue: what you are buying

Scalar common blue is a blue colour form of the freshwater angelfish, Pterophyllum scalare, a tall-bodied cichlid from the Amazon basin. Each purchase is one live fish in the size you select, from 1 cm juveniles to fish of more than 7 cm. Whichever size arrives, plan for the adult: FishBase records a maximum of 15 cm in total length, and the long fins make a grown angelfish taller than it is long, so it needs a tall, mature aquarium of around 200 litres and the company of its own kind.

The species is well documented. FishBase places it in the cichlid family Cichlidae, describes it as one of the most popular of all tropical aquarium fish and gives its IUCN status as Least Concern. "Scalar common blue" is the trade name for this blue form, and there is no evidence that one colour form is hardier or calmer than another, so the care on this page applies to the species as a whole.

Why the colour sits outside the brackets

The title follows a simple rule: the scientific name in brackets identifies the species, and the words before it describe the form you are buying. Colour names such as "common blue" belong to domestic strains rather than to the scientific name, which is why silver, marble, koi and blue angelfish all share the name Pterophyllum scalare and the same care.

At a glance

Choosing a size

The size you select is the size supplied, not the adult size. Nine sizes appear on this listing: 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) and XXL (more than 7 cm). Sizes sell out and return, so the size menu is the place to see what can be ordered.

Smaller fish are younger, and they need exactly the same adult-sized plan because they will grow into it. They are also small enough to be eaten by larger tank mates, so keep them away from big or boisterous fish until they have grown. Larger sizes bring you closer to the adult, but even an XL fish has a long way to grow before it reaches full length and height.

Buying for a pair or group

Each purchase supplies one fish, so order two or more if you are starting a pair or group. Because young angelfish cannot be sexed reliably, two juveniles bought together may not become a pair. Seriously Fish suggests growing on a group of six juveniles if you want a pair to form naturally, which works only if you have the room, or a rehoming route, for the fish that do not pair off.

Is it the right fish for your aquarium?

• Yes, if you have, or are planning, a tall aquarium of around 200 litres that is fully cycled, with ammonia and nitrite reading zero.
• Yes, if you want a pair or a planned group and have a second tank or a rehoming route ready in case adults fall out.
• Not yet, if the tank is shallow or only big enough for the juvenile you would receive.
• No, if the aquarium holds small tetras, shrimp or other animals small enough to be eaten.

To compare other colour forms of the same species, browse our angelfish collection.

Before you order

Sex is guaranteed only when the selected option explicitly states male or female. This Scalar common blue listing has no sex-guaranteed option. Angelfish are difficult to sex until they spawn, so a pair cannot be picked reliably from young fish.

Gallery images have been digitally enhanced to improve image quality. Natural colour, pattern, size and maturity can vary between live animals.

Species, colour form and wild origins

An accepted, well-documented species

The accepted name is Pterophyllum scalare (Schultze, 1823). Eschmeyer's Catalog of Fishes places it in the family Cichlidae and records the lower Amazon in Brazil as its type locality. FishBase gives its native distribution as the Amazon River basin in Peru, Colombia and Brazil, along the Ucayali, Solimões and Amazon rivers, together with rivers of Amapá in Brazil, the Rio Oyapock in French Guiana and the Essequibo River in Guyana.

Where it lives in the wild

FishBase describes adults living in swamps and flooded ground where aquatic and riverside vegetation is dense and the water is either clear or silty, and notes that the fish's colour is deeper in clear water. Those records describe a wild habitat rather than a recipe for an aquarium, but they explain why angelfish look at home among tall plants and upright wood.

What "Scalar common blue" means

Domestic angelfish are kept in many colour and fin forms. Seriously Fish mentions black, gold and koi strains alongside the standard silver, and our angelfish care guide lists marble, platinum, zebra, smokey and long-fin forms among others. "Scalar common blue" is the trade name for a blue form of the same species. Choose an individual fish for its health and your aquarium for its adult needs; colour makes no difference to either.

It is worth knowing that the altum angelfish, Pterophyllum altum, is a separate species rather than a colour form, so its care should not be assumed to match this fish.

Adult size, height and aquarium planning

How big an adult gets

FishBase gives a maximum length of 15 cm total length in its biology notes and lists 10.5 cm total length for males or unsexed fish in its length record; Seriously Fish quotes 150 mm standard length. For planning, use about 15 cm. Length is only half the story, though: the tall dorsal and anal fins can make an adult roughly 20–25 cm from fin tip to fin tip, and individual fish and domestic strains vary.

Tank size and height

Height matters as much as volume. OATA's care sheet for American cichlids recommends at least 120 litres for a pair of the smaller species under 15 cm and adds that angelfish need an aquarium that is sufficiently tall when they are fully grown. Seriously Fish treats 100 × 40 × 50 cm, about 200 litres, as the smallest aquarium to consider and recommends at least 50 cm of height for adults, while FishBase gives a minimum aquarium length of 100 cm.

Our freshwater angelfish care guide sets out the store's planning point: roughly 200 litres, a 100 × 40 cm footprint and about 50 cm of usable height for an adult pair, with more room and an exit plan for a group. OATA also suggests allowing 40 litres per adult when stocking shoaling species such as angelfish, which is a useful cross-check on numbers but says nothing about the height an adult needs.

Filter, heater and flow

For its 200-litre recommendation, Seriously Fish suggests a filter rated at around 800–1,000 litres per hour, a turnover of four to five times the tank volume each hour, and roughly 200–275 W of heating in a room of about 20 °C. It also notes that angelfish prefer gentle water flow, so position outlets to avoid a strong current across the open water. Choose filtration for water quality and oxygen exchange, cover any intake that could catch a long fin, and fit a secure lid.

Layout and décor

Seriously Fish recommends a well-planted tank with tall, leafy plants such as Amazon swords. Upright plants and wood break the tank into separate areas and interrupt long lines of sight between rivals, while open water lets an adult turn without catching its fins. OATA's American cichlid sheet recommends fine gravel or sand because many species will dig or sift the substrate when feeding or breeding, so bed heavy décor firmly on the base and avoid sharp edges near those long fins.

Preparing the tank

Mature the filter before any fish arrive, and confirm by testing rather than by the calendar that ammonia and nitrite read zero. Our guide to setting up and maturing a first tropical tank walks through the process. Check the temperature with a thermometer rather than relying on the heater dial alone.

Water chemistry and stability

Published water values for angelfish differ because they describe different things, from recorded wild conditions to general trade guidance. Seeing them side by side makes the routine target easier to understand.

Why the routine target is narrower

The routine target keeps to the ground where FishBase's species ranges and OATA's group guidance overlap, the same approach our care guide takes. The top of FishBase's temperature range describes the environment the species has been recorded in, not a temperature to hold all year, and the OATA care sheet for American cichlids presents its figures as a general guide for a whole group of fish. Staying inside the overlap leaves you a margin on both sides.

Stability first

Match the water the fish comes from as closely as you reasonably can, acclimatise gradually and avoid abrupt changes. OATA stresses that American cichlids can be stressed by even the smallest amounts of ammonia, so ammonia and nitrite must stay at zero and nitrate no more than 20 mg per litre above your tap water.

If you do need to adjust pH or hardness, do it slowly and by measurement. Tap water and reverse-osmosis water vary too much for a fixed mixing recipe, so measure GH, KH and pH before and after any change. Keep such adjustments for planned changes; they are never the fix for an ammonia or nitrite problem, which needs urgent attention and advice instead.

A worked example

Suppose your tap water tests at pH 7.6 and 10 dGH, and your heater holds 25 °C. Every value sits inside the routine target, so leave the chemistry alone and concentrate on keeping it steady from one water change to the next. If the same water tested at 16 dGH instead, it would sit above both OATA's guide and the routine target; softening it would mean measured mixing with reverse-osmosis water, planned and settled before the fish arrive rather than carried out around them.

Testing and tools

Our guide to testing aquarium water and reading GH, KH and pH explains each measurement. Once you have your own results, the water parameter matcher gives a quick comparison, but keep the angelfish target above as your guide.

Feeding from juvenile to adult

What to feed

Angelfish are omnivores. Seriously Fish notes that wild fish feed predominantly on small crustaceans and other aquatic invertebrates, while tank-bred fish will accept pellet or flake food and relish live or frozen foods. OATA adds that American cichlids often prefer meaty foods. A complete cichlid pellet or granule, or a suitable flake, sized so every fish can swallow it, makes the staple; frozen or freeze-dried daphnia, brine shrimp and bloodworm add variety.

Portions and routine

Feed only what the fish eat within a few minutes, once a day, as OATA recommends for American cichlids. These fish can eat large amounts in one sitting, so take care not to overfeed: uneaten food and extra waste break down and release toxic compounds into the water. Remove leftovers after each meal, and watch that every fish, including quieter or lower-ranking ones, gets its share.

Why variety matters

A controlled study of freshwater angelfish by Kasiri, Farahi and Sudagar (2012) compared different feed types and found that they affected growth and reproductive performance. That supports offering a varied, good-quality diet, but it does not set a single household menu. Treat bloodworm and other favourites as part of the mix rather than the whole diet.

Feeding small juveniles

If you choose one of the smallest sizes, the same rules apply with smaller particles. Crumble or choose food fine enough for the fish to take whole, and watch body shape over the following weeks: a steady, rounded profile tells you the portions are right, while a pinched belly or leftovers on the substrate tell you to adjust.

Maintenance and health checks

A weekly routine

• Change 25% of the water at least once every week, as OATA strongly recommends, siphoning solid waste from the gravel as you go.
• Test the water at least once a week, and more often after adding fish, so that ammonia and nitrite never build up.
• Treat replacement water with tap water conditioner to remove chlorine or chloramine.
• Check the filter for blockages. If the media needs cleaning, rinse it lightly in tank water removed during the water change, never under the tap.

The right water-change volume also depends on how many fish you keep, how much you feed, the plants and the filter, so treat OATA's 25% as a starting routine and let your test results guide any adjustment.

What healthy looks like

A healthy angelfish swims steadily, breathes at an even rate, has clear eyes, holds its fins open and undamaged, keeps a normal body shape and feeds reliably. The RSPCA's fish health and welfare advice covers the same visible signs and puts water quality first whenever something changes.

Warning signs

OATA's watch list covers changes in swimming (hanging at the surface, sitting on the bottom or moving erratically), colour, temperament, breathing rate, appearance (white spots, fluffy growths, loss of fins or scales), body condition and appetite. Clamped fins, gasping, flashing, wounds and poor balance also deserve attention. Treat all of these as signals to investigate, not as a diagnosis.

If something changes

1. Test ammonia, nitrite, nitrate and temperature straight away, and pH where relevant.
2. Treat any detectable ammonia or nitrite as urgent, and avoid sudden elective changes to pH, hardness or temperature.
3. Move an affected fish only if a separate, mature tank is ready and the move will not add stress.
4. Photograph the signs, note when they started, and contact us or a fish vet for advice.
5. In the UK, use only a lawful treatment labelled for fish and for your type of system, following its instructions or a vet's direction.

Avoid copying temperature-raising or medication recipes found online: the right response depends on a confirmed problem, the fish and the water.

Quarantine and accidents

Our care guide recommends having a mature quarantine set-up, with its own equipment, before adding new fish to an established community. If an angelfish ever jumps out, return it to aquarium water straight away using wet hands or a wet, soft net, handle it as little as possible and watch its breathing, balance and skin for injury. Then check the lid, and get fish-vet advice if recovery looks abnormal.

Why the filter matters

The RSPCA's aquarium environment guidance explains that no fish should be kept without a well set up and maintained filter. Fish release ammonia, which is toxic; beneficial bacteria in a working filter convert it to nitrite, which is also toxic, and then to nitrate, which is safer. Keeping that bacterial population healthy is the core of every routine above.

Sexing and breeding

Telling males from females

Angelfish are difficult to sex. Seriously Fish explains that males have a smaller, pointed genital papilla, but this can usually be seen only when the fish are spawning, and that behaviour may be a better clue, because males in breeding condition are likely to be more aggressive and territorial. Forehead shape, fin angle and general temperament are not reliable ways to sex young fish. OATA makes the wider point that some American cichlids show no visible difference unless they are breeding.

How pairs form

If you intend to breed, Seriously Fish suggests starting with a group of six juveniles so that a pair can form. Research on the species supports serial monogamy under captive conditions, which means a pair may separate and re-pair rather than stay together for life.

Spawning and parental care

Angelfish lay adhesive eggs on a vertical or firm surface such as slate, a broad leaf or even the aquarium glass. Condition a pair with live foods such as bloodworm and brine shrimp. Both parents may guard the eggs and then the fry, but keep the adults well fed, as they are known to eat their young at times. Seriously Fish notes that fry can take newly hatched brine shrimp once they have absorbed their yolk sacs, usually after about two days, before moving on to a commercial fry food.

Breeding sharpens territorial defence, so a pair that spawns in a community tank can make life difficult for everything else in it. A separate, mature breeding set-up is the safer plan if you want to raise young.

Delivery and the first weeks at home

Packing and courier

Your angelfish is hand-packed by our team and bagged in pure oxygen inside an insulated poly box, with a heat pack when the weather calls for it. We email the tracking number and your confirmed delivery date, and a licensed live-animal courier delivers the parcel. Someone must be at home to receive it, because live fish cannot be left unattended. Our delivery and Live Arrival Guarantee policy has the full details.

On the day

1. Take the parcel in yourself on the confirmed delivery day.
2. Film a continuous unboxing video before anything is disturbed: the sealed parcel with the outer box in view, the opening in one unbroken take, and the fish still in its sealed bag. Open and inspect the parcel the same day; the video is needed for any Live Arrival Guarantee claim.
3. Acclimatise your fish slowly by floating the sealed bag in the aquarium for 20–30 minutes before releasing it.
4. Release the angelfish without pouring the bag water into your tank.
5. If there is a problem, contact us the same day, WhatsApp being the fastest route, with your order number and the unboxing video, and we will arrange a replacement or refund.

The first weeks

Each new fish adds waste that the filter's bacteria must catch up with, which is why OATA advises raising numbers slowly. Stocking too quickly can bring on new tank syndrome, with unhealthy levels of ammonia and nitrite that may cause fish to become ill and die. Test more often than usual for the first few weeks, feed modestly and add any further fish gradually.

If you are building a pair or group, watch the fish closely as they settle. Short displays are normal cichlid behaviour, but a fish that is repeatedly chased from food or pinned in a corner needs separating before it is harmed.

Tank mates, pairs and groups

Living with other angelfish

Angelfish should not be kept alone. OATA notes that they are social and that those kept singly may become stressed, and it recommends a group or, at minimum, a pair. FishBase suggests keeping them in groups of five or more. The complication is that angelfish, although generally peaceful, may squabble with their own kind, as Seriously Fish points out, and adults sort themselves into a social order that affects who eats first and who gets chased.

• A compatible pair is a workable plan for an adult aquarium, but two fish chosen at random are not automatically a pair and may fight.
• A juvenile group lets pairs form naturally, but the adults then need much more space and close watching.
• A single fish should not be the default, given OATA's warning about stress.

Whichever route you take, have a second tank or a realistic rehoming route ready before trouble starts. A fish that is persistently kept away from food or cover has a welfare problem that needs acting on.

Fish to avoid

• Small fish, shrimp and fry. Seriously Fish warns that angelfish may eat small fish such as tetras, and very small tetras, shrimp and fry stay at risk however calm the angelfish seems.
• Persistent fin-nippers. Long dorsal, anal and ventral fins are an easy target.
• Highly aggressive or much faster-feeding species. These can keep angelfish stressed and short of food. OATA advises that the more aggressive American cichlids be kept alone or only with equally aggressive cichlids.

Companions worth considering

OATA describes angelfish and severums as calmer American cichlids that can share a robust community aquarium with larger shoaling species. Corydoras and bristlenose plecos are often considered because they spend their time at a different level of the tank, but that is a starting point for research rather than an assurance: check each fish's adult size, floor space needs and water range against your aquarium.

Planning numbers in a 200-litre tank

OATA's allowance of 40 litres per adult angelfish means five adults would fill a 200-litre aquarium on their own, with no margin left for companions. That is why our care guide treats about 200 litres as the plan for an adult pair, and asks for more room and an exit plan for a group. In practice, a tank of that size suits a pair of angelfish with a modest number of larger, peaceful shoaling fish, added gradually as the filter keeps pace.

Five checks before adding any companion

If a companion fails any one of these checks, choose something else. A calm, well-matched community is easier to keep healthy than one that needs constant watching.

Scalar common blue questions answered

How big does a Scalar common blue angelfish get?

Plan for about 15 cm in total length, the maximum FishBase records for Pterophyllum scalare, with the long fins making an adult roughly 20–25 cm tall. Size the aquarium around the adult fish rather than the juvenile you receive.

What size aquarium does Pterophyllum scalare need?

Plan on about 200 litres with at least 50 cm of height for adults. Seriously Fish gives 100 × 40 × 50 cm as the smallest aquarium to consider, and OATA's general floor of 120 litres for a pair of smaller American cichlids comes with a warning that angelfish need a sufficiently tall tank.

How many angelfish should I keep together?

Keep a compatible pair or a planned group rather than a single fish; OATA notes that angelfish kept singly may become stressed. FishBase suggests groups of five or more, but adults may squabble with their own kind, so a group needs more space and a plan for separating fish.

Is Scalar common blue a good fish for beginners?

It suits a prepared keeper rather than a first set-up. We rate its care as intermediate: it needs a mature, tall aquarium, tested water and a plan for aggression within pairs or groups.

What do angelfish eat?

Pterophyllum scalare is an omnivore that often prefers meaty foods. Use a complete cichlid pellet, granule or suitable flake as the staple, add frozen or freeze-dried daphnia, brine shrimp and bloodworm for variety, and feed only what is eaten within a few minutes, once a day.

What temperature and pH does a Scalar common blue need?

Aim for a routine 24–27 °C, pH 6.5–8.0 and about 5–12 dGH, where FishBase's species ranges overlap OATA's broad guidance for American cichlids. Keep conditions stable and make any change gradually.

Are angelfish aggressive, and do they nip fins?

They are generally peaceful cichlids but may squabble with their own kind, and pairs defend territory more strongly when breeding. Their own long fins are a target, so avoid persistent fin-nippers as tank mates.

Which fish can live with Pterophyllum scalare?

OATA says calmer American cichlids such as angelfish can share a robust community aquarium with larger shoaling species. Corydoras and bristlenose plecos are often considered, but check their adult size, floor space and water needs. Very small tetras, shrimp and fry are at risk of being eaten.

How does a Scalar common blue arrive alive in the UK?

It is hand-packed, bagged in pure oxygen inside an insulated poly box, with a heat pack when the weather calls for it, and carried by a licensed live-animal courier. Be in to receive it, film a continuous unboxing video from the sealed parcel onwards, then float the sealed bag for 20–30 minutes before releasing the fish without the bag water.

Sources and further reading

The identity, care and welfare information on this page draws on these public sources.

• FishBase: Pterophyllum scalare, for identity, native distribution, wild habitat, recorded environment and length.
• Eschmeyer's Catalog of Fishes: Pterophyllum scalare, for the accepted name, authorship, family and type locality.
• Seriously Fish: Pterophyllum scalare, for aquarium size, water, diet, behaviour, sexing and breeding.
• OATA: How to look after American cichlids, for group water guidance, tank sizes, feeding, maintenance and compatibility.
• Kasiri, Farahi and Sudagar (2012), feed types and angelfish growth and reproduction, a controlled feeding study.
• RSPCA: fish environment and RSPCA: fish health and welfare, for filtration and health signs.
• Tropical Fish Co's freshwater angelfish care guide and delivery policy, both linked in the care tab.