Pterophyllum scalare blue marble

Blue marble angelfish: what you are buying

Pterophyllum scalare blue marble is a marbled colour form of the freshwater angelfish, the tall, disc-shaped South American cichlid that FishBase describes as one of the most popular of all tropical aquarium fish. Its body and fins carry dark, irregular marbling broken by paler patches that can shine blue under aquarium light. Underneath the pattern it is the same species as the silver, koi, gold and black angelfish, with the same need for height, space, stable water and a sensible social plan.

This is a fish to buy for the aquarium it will grow into, not the one that suits it on the day it arrives. A juvenile of a few centimetres looks modest, yet adults are planned at around 15 cm long and 20–25 cm tall once the long dorsal and anal fins have grown. That height, more than any other single figure, decides whether a tank is suitable.

What one purchase supplies

Each purchase supplies one live blue marble angelfish at the size you choose. Three dispatch sizes are offered: 3–3.5 cm, 4–5 cm and L (5.5–6 cm). The size you select is the size supplied, not the adult size. All three are young fish with most of their growing still ahead of them, so the choice mainly affects how far along the fish is when it reaches you rather than the aquarium you will eventually need.

If you are planning a pair or a group, each fish is a separate purchase, so add the number you intend to keep. Sex is guaranteed only when the selected option explicitly states male or female. This Pterophyllum scalare blue marble listing has no sex-guaranteed option. Angelfish are hard to sex from the outside, which is why pairs are usually allowed to form within a group of young fish rather than picked as two individuals.

Who this angelfish suits

The blue marble pattern

Marble angelfish are a domestic colour form of Pterophyllum scalare, kept and bred in aquariums for their pattern rather than found as a separate wild fish. On a blue marble the dark marbling can cover much of the body and trail into the fins, with lighter scales and blue or turquoise tones showing through. Every fish carries its own arrangement of markings, so two blue marbles bought together will not look identical.

The gallery photograph shows a well-grown fish with long, trailing fins. The fish supplied is a juvenile at the size you choose and has not yet reached those proportions. Gallery images have been digitally enhanced to improve image quality. Natural colour, pattern, size and maturity can vary between live animals.

Does colour change the care?

No colour form of Pterophyllum scalare is known to be hardier, calmer or more disease-resistant than another, so a blue marble needs exactly the same tank, water and social planning as a silver or koi angelfish. Choose it because you like the pattern, then judge the individual fish, its size and its condition in the usual way. Because every colour form is the same species, fish of different forms can be planned together as one group under the same social rules.

FishBase notes that wild angelfish show deeper colour in clear water. In the aquarium, clean, well-filtered water and a planted layout are the practical way to let a marble's blue tones show, and they suit the fish's welfare as well.

Four decisions to make before ordering

• Height and volume: a tall aquarium of around 200 litres is our planning figure for an adult pair, with more room for a group.
• Social plan: a compatible pair or a group, never a lonely single fish by default.
• Companions: nothing small enough to be swallowed and nothing that nips long fins.
• A mature tank: zero ammonia and nitrite confirmed by testing before the fish arrive.

Our freshwater angelfish care guide covers the species in more depth, and you can compare this fish with the other colour forms in our angelfish collection.

Size now and size later

Name and origin

The accepted scientific name is Pterophyllum scalare (Schultze, 1823), placed in the cichlid family Cichlidae; Eschmeyer's Catalog of Fishes records its authorship, type locality and distribution. The native range covers the Amazon basin in Peru, Colombia and Brazil, along the Ucayali, Solimões and Amazon rivers, together with rivers of Amapá in Brazil, the Oyapock in French Guiana and the Essequibo in Guyana. Blue marble is a trade name for the colour form, not a separate species; the altum angelfish, Pterophyllum altum, is a different species altogether.

The three dispatch sizes

The three sizes are measured on young fish: 3–3.5 cm, 4–5 cm and L (5.5–6 cm). At 3 cm a blue marble is a small juvenile, a long way from its adult height. Choose whichever size suits your tank and plans, but buy the aquarium for the adult. If you are building a group, buying every fish at one size lets you watch them grow up together.

How big an adult gets

Published adult sizes for this species are measured in different ways, so it helps to know where each figure comes from. FishBase records a maximum of 15 cm total length for Pterophyllum scalare, alongside a smaller current field record of 10.5 cm total length for a male or unsexed fish. Seriously Fish gives an adult length of 150 mm measured as standard length. Our own planning figure takes the larger number: expect an adult of about 15 cm long.

Length is only half the story. The dorsal and anal fins of an adult angelfish extend far above and below the body, so a fish around 15 cm long can stand roughly 20–25 cm tall from fin tip to fin tip. That is the measurement that makes a shallow tank unsuitable, even one with plenty of litres.

Lifespan and long-term commitment

OATA notes that American cichlids, the group that includes angelfish, can live for several years in a well-matured set-up with good water quality. Treat a blue marble as a fish you will keep for years rather than a short-term display, and plan the aquarium, the social group and your holiday cover with that in mind.

Planning the aquarium

Volume and footprint

Seriously Fish suggests an aquarium of 100 × 40 × 50 cm, around 200 litres, as the smallest to consider for adult angelfish, and FishBase lists a minimum aquarium length of 100 cm. Our planning figure matches that: roughly 200 litres, a footprint of about 100 × 40 cm and around 50 cm of usable height for an adult pair. A group, or a community with other sizeable fish, needs more room than that and a plan for moving fish if trouble starts.

OATA, the UK ornamental fish trade body, sets a lower floor of 120 litres for a pair of smaller American cichlids and adds that angelfish need an aquarium that is sufficiently tall when fully grown. For shoaling species such as angelfish it also suggests allowing 40 litres per adult fish when stocking. Use that figure as a check on total stocking, not as permission to fill a smaller tank.

Height and turning room

A tall tank on its own is not enough. An adult angelfish needs depth for its fins and enough open water to turn without dragging them against glass or decor. Seriously Fish recommends a tank at least 50 cm tall for adult fish. Leave a clear band of water above the substrate and below the surface rather than filling the height with ornaments.

Layout, plants and substrate

Wild angelfish live among dense aquatic and riverside vegetation in swamps and flooded ground, in water that is either clear or silty. In the aquarium, Seriously Fish advises a well-planted tank with tall, leafy plants such as Amazon swords. Vertical plants or bogwood break up sight lines between rival fish and give a pair somewhere to settle, while open water in front keeps swimming space free.

• Use fine gravel or sand: OATA notes that many American cichlids will dig or sift the substrate when feeding or breeding.
• Secure rock and wood so digging cannot topple it, and avoid sharp edges near long fins.
• Broad leaves, slate or smooth vertical surfaces give a pair a place to spawn later on.
• Fit a secure lid, and cover any hazardous intake so long fins cannot be drawn in.

Filtration, flow and heating

Angelfish prefer gentle water movement, but gentle never means stagnant. Seriously Fish suggests a turnover of four to five times the tank volume an hour, which for about 200 litres means a filter rated at roughly 800–1000 litres per hour, with the outflow spread so the fish are not pushed around. The same profile estimates around 200–275 W of heating to hold the temperature in a tank that size, assuming a room of about 20 °C. Check the water with a thermometer rather than trusting the heater dial alone.

Mature the aquarium first

Set the tank up, cycle the filter and confirm zero ammonia and nitrite with a test kit before any angelfish arrives; a calendar alone cannot tell you a tank is ready. Our guide to setting up and maturing a first tropical aquarium walks through the process step by step.

Water quality and routine care

Routine targets

Where the numbers come from

FishBase lists Pterophyllum scalare at 24–30 °C, pH 6.0–8.0 and 5–13 dH, while Seriously Fish gives 24–30 °C, pH 6.0–7.4 and 0–15 dGH. OATA's care sheet for American cichlids as a whole suggests 22–27 °C, pH 6.5–8.0 and 4–12 °dH, and asks keepers to check species needs with their retailer. Our routine target sits where FishBase and OATA overlap. Seriously Fish's profile gives a softer, more acidic pH band, so water between pH 6.5 and 7.4 falls inside every range listed here; there is no need to push pH upwards towards 8.0.

Stability matters more than chasing an exact figure. Match the water the fish has been living in, make any change gradually and measure rather than guess. Reserve slow adjustments for planned changes to pH, hardness or temperature; a rise in ammonia or nitrite is an emergency to deal with straight away, not something to correct over days.

If GH, KH and pH are unfamiliar, our guide to aquarium water chemistry explains what each value means and how to test it. Once you have readings, the water parameter matcher lets you compare them with published ranges. Avoid copying a fixed mix of reverse-osmosis and tap water from elsewhere: tap water differs from place to place, so test your own before deciding anything.

Filtration and the nitrogen cycle

The RSPCA is clear 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 biological filter convert it to nitrite, which is also toxic, and then to nitrate, which is safer. A cichlid the size of an adult angelfish eats and excretes more than a small community fish, so a filter sized for the adult tank is worth fitting from the start.

Water changes and testing

1. Test ammonia, nitrite and nitrate regularly; OATA recommends at least once a week.
2. Change water often: OATA strongly recommends a partial water change of 25% at least once every week, using a siphon to lift waste from the gravel.
3. Treat replacement water with a tap-water conditioner to remove chlorine or chloramine before it goes in.
4. Check the filter for blockages. When the media needs cleaning, rinse it lightly in tank water removed during the water change, never under the tap, so the bacteria survive.

OATA's care sheet points out that American cichlids can be stressed by even small amounts of ammonia. Let your test results, stocking and feeding decide whether the routine needs tightening; cloudy water is a late warning, not the first one.

Feeding

What angelfish eat

Seriously Fish describes Pterophyllum scalare as omnivorous. Wild fish feed mainly on small crustaceans and other aquatic invertebrates, but tank-bred angelfish are far removed from their wild ancestors and accept pellet or flake food, while relishing live or frozen foods. OATA makes a similar point for American cichlids generally: they are omnivores that often prefer meaty foods.

A practical routine

Build the diet around a good-quality cichlid pellet, granule or flake sized so the fish can swallow it easily; for a 3–3.5 cm juvenile that means small granules or crumbled flake. Add frozen or freeze-dried foods such as daphnia, brine shrimp and bloodworm for variety. OATA's general guidance for American cichlids is to feed only what the fish will eat within a few minutes, once a day, because they can eat a lot in one sitting and uneaten food quickly pollutes the water.

• Watch every fish eat, including quieter or lower-ranking fish that may hang back.
• Remove leftovers after feeding rather than letting them rot in the gravel.
• Judge portions by body shape over weeks: a gently rounded belly, not a swollen one.
• Keep bloodworm, brine shrimp and similar treats as extras, not the whole diet.

Why variety matters

A controlled study of freshwater angelfish by Kasiri, Farahi and Sudagar (2012) found that the type of food offered affected growth and reproductive performance. That result supports a varied diet built on a complete staple; it does not set one menu or schedule for every home aquarium. If you are conditioning a pair for spawning, Seriously Fish suggests live foods such as bloodworm and brine shrimp.

Feeding in a community

In a community, fast surface feeders can take most of the food before a slower or subordinate angelfish gets its share. Spread food across the surface, feed a little at a time and check that each angelfish eats. A fish that repeatedly misses meals loses condition, and that shows in its body shape before anything else.

Arrival, acclimatisation and the first weeks

When the parcel arrives

Your blue marble travels bagged by hand in pure oxygen inside an insulated box, with a heat pack when the weather calls for it, and is carried by a licensed live-animal courier. We email the tracking number and your confirmed delivery date so you know when to be in. The full policy is on our delivery and Live Arrival Guarantee page; the steps below follow it.

1. Make sure someone is at the delivery address to receive the parcel; live fish cannot be left unattended.
2. Before anything is disturbed, start a continuous unboxing video: show the parcel still sealed with the outer box visible, open it in one take, and film the fish still inside the sealed bag.
3. Float the sealed bag in your aquarium for 20–30 minutes to acclimatise the fish slowly.
4. Release the angelfish into the aquarium, and never pour the bag water into your tank.
5. If anything has gone wrong, contact us the same day, with WhatsApp the fastest route, sending your order number and the unboxing video so we can arrange a replacement or refund.

The Live Arrival Guarantee also needs the parcel to be opened and inspected on the day it arrives.

The first few weeks

Give a newly arrived angelfish time to settle. Over the following days, look for steady swimming, regular breathing, open fins and interest in food. Test the water more often than usual in the first weeks, because a new fish adds to the load on the filter.

OATA advises increasing the number of fish in an aquarium slowly, because the filter bacteria need time to catch up each time stocking and feeding rise. Adding too many fish too quickly can cause new tank syndrome, with ammonia and nitrite climbing to harmful levels.

Quarantine before mixing

If the angelfish is joining an established tank, a separate, mature quarantine aquarium is the careful route. The veterinary guidance summarised in our care guide recommends at least 30 days with separate equipment. That gives time to watch for problems before a newcomer shares water with fish you already keep.

Health checks and when to act

Signs of a settled, healthy angelfish

A healthy angelfish swims steadily, breathes at a regular rate, has clear bright eyes, undamaged fins, intact scales and a consistent body shape, and feeds reliably. Its colour stays consistent from day to day.

Changes worth acting on

OATA's list of what to watch covers most early warnings. Look for fish hanging at the surface, sitting on the bottom or swimming erratically; colour turning darker or paler than normal; more aggression or hiding than usual; gill covers moving faster or slower than normal; white spots, fluffy growths, lost scales or damaged fins; weight loss or bloating; and reduced interest in food.

What to do first

1. Test ammonia, nitrite, nitrate and temperature, and pH where relevant, straight away.
2. Treat any detectable ammonia or nitrite as urgent and correct it before anything else.
3. Move an affected fish only if a mature, suitable separate tank is ready.
4. Photograph the signs, note when they started and seek 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 veterinary direction.

The RSPCA fish health advice takes the same approach: check water quality first, then look closely at what has changed. Signs such as white spots or head lesions need a diagnosis rather than a remedy copied from a forum, and there is no safe one-size-fits-all temperature treatment for white spot.

If a fish jumps out

Return it to suitable aquarium water immediately with wet hands or a wet, soft net, keeping it out of water for as short a time as possible. Watch its breathing, balance and any visible injury, check the lid for gaps, and get fish-vet advice if recovery looks abnormal.

Pairs, spawning and sexing

How pairs form

Blue marble angelfish are quite difficult to sex. Seriously Fish notes that males have a smaller, pointed genital papilla, but this usually shows only when the fish are spawning; behaviour can be a better clue, as males tend to be more territorial in breeding condition. For anyone hoping to breed, the same profile suggests starting with a group of six juveniles and letting a pair form among them.

A behavioural study summarised in our care guide supports serial monogamy under its captive conditions, which means a pair can change partners. "Mates for life" is too strong a promise.

Spawning and parental care

• Pairs lay eggs on vertical surfaces such as slate, broad-leaved plants or even the aquarium glass.
• Both parents may guard the eggs and then the fry once they hatch.
• Keep the adults well fed; Seriously Fish warns that angelfish sometimes eat their fry.
• Fry can take newly hatched brine shrimp once the yolk sac has been absorbed, usually after about two days, before moving on to commercial fry food.

Plan for the change in behaviour

Breeding sharply increases territorial defence. A spawning pair may chase tank mates away from its chosen site, including other angelfish. A dedicated, mature breeding tank gives the pair and any fry a safer arrangement than a busy community aquarium, and clutch size and hatching time vary from pair to pair.

One fish, a pair or a group?

A single angelfish is not the default

OATA advises that angelfish should be kept in groups or as a pair at minimum, because they are social and fish kept singly may become stressed. Seriously Fish describes the species as generally peaceful for a cichlid but likely to squabble with its own kind, and suggests small groups. FishBase notes aquarium keeping in groups of 5 or more, with pairs kept in smaller tanks for breeding.

Choosing between a pair and a group

As young angelfish mature, a social ranking develops and a pair may claim part of the tank. More fish does not automatically mean less aggression; what matters is whether every fish can feed, rest and move without being cornered.

Signs the arrangement is not working

• One fish persistently excluded from food or pushed into a corner.
• Split or ragged fins, especially on a smaller or subordinate fish.
• Constant chasing rather than brief displays that settle.
• A fish that stays hidden while the others hold the open water.

Persistent exclusion is a welfare problem, not a hierarchy to ignore. Have a second mature tank or a realistic rehoming route ready before you need it.

Choosing tank mates

The checks that matter

OATA considers calmer American cichlids such as angelfish suitable for a robust community aquarium with larger shoaling species, provided water needs overlap. Use these checks for every proposed companion.

Fish to leave out

• Small fish: Seriously Fish warns that angelfish may eat small fish such as tetras, and a companion too big to swallow now may not stay that way as the angelfish grows.
• Shrimp and fry: both remain at risk of being eaten.
• Fin-nippers: long angelfish fins are an easy target.
• Highly aggressive cichlids: OATA advises keeping the more aggressive American cichlids alone or with equally aggressive species.

Companions to consider with care

Larger, robust shoaling fish that share the angelfish's water preferences are the kind OATA describes. Bottom-dwellers such as corydoras and bristlenose plecos are often considered because they use a different level of the tank, but species, adult size, floor space and water needs still have to fit. No companion is guaranteed safe; individual temperament and breeding behaviour can change the picture.

Species tank or community?

A community works best when every fish is robust, larger than an angelfish's mouth at adulthood and happy in the same water. A species tank holding only angelfish removes most of those compromises and makes it easier to watch how a group is getting on, which matters most in the months when young fish are pairing off and claiming territory.

Live plants

OATA notes that American cichlids may dig up or eat live plants. Angelfish are among the calmer members of the group, and Seriously Fish recommends a well-planted tank for them, but anchor plants firmly and watch for damage in the first months.

Blue marble angelfish questions

How big does a Pterophyllum scalare blue marble angelfish get?

Plan for an adult of about 15 cm total length and roughly 20–25 cm tall including the long dorsal and anal fins. FishBase also holds a smaller field record of 10.5 cm, but the larger figure is the safer basis for choosing a tank.

What size aquarium does a blue marble angelfish need?

We plan around 200 litres with a footprint of about 100 × 40 cm and roughly 50 cm of usable height for an adult pair of Pterophyllum scalare, matching Seriously Fish's smallest recommended tank. A group needs more room than a pair.

How many angelfish should I keep together?

Keep a compatible pair or a group rather than one fish on its own. OATA warns that angelfish kept singly may become stressed, and FishBase notes groups of 5 or more in aquariums. Two fish chosen at random are not automatically a pair.

Is a Pterophyllum scalare angelfish suitable for beginners?

We rate Pterophyllum scalare as intermediate. It suits a prepared keeper with a mature, tall aquarium, a regular testing routine and a plan for pairing or aggression, rather than someone setting up a first small tank.

What do angelfish eat?

Feed a quality cichlid pellet, granule or flake sized for the fish, with frozen or freeze-dried daphnia, brine shrimp or bloodworm for variety. OATA's general guidance for American cichlids is to feed only what is eaten within a few minutes, once a day.

What temperature and pH does Pterophyllum scalare need?

Our routine guidance is 24–27 °C, pH 6.5–8.0 and 5–12 dGH, where FishBase species values and OATA's American-cichlid guidance overlap. Match the water the fish has been kept in and make any change gradually.

Is a Pterophyllum scalare blue marble aggressive, or does it nip fins?

It is generally peaceful for a cichlid but may squabble with its own kind, and pairs become territorial when spawning. Its long fins can attract fin-nipping fish, so leave known fin-nippers out of the tank.

Which fish can live with Pterophyllum scalare?

OATA describes angelfish living in a robust community with larger shoaling species that share their water needs. Leave out fish small enough to swallow, such as small tetras, along with shrimp, fin-nippers and highly aggressive cichlids.

How does a Pterophyllum scalare blue marble arrive alive in the UK?

It is bagged by hand in pure oxygen in an insulated box, with a heat pack when needed, and carried by a licensed live-animal courier. Be at home, film a continuous unboxing video from the sealed parcel, then float the sealed bag for 20–30 minutes before releasing the fish. Contact us the same day with your order number and video if anything is wrong.

Sources and further reading

• FishBase: Pterophyllum scalare, freshwater angelfish: identity, family, native range, recorded lengths and environmental ranges.
• Eschmeyer's Catalog of Fishes: Pterophyllum scalare: accepted name, authorship, family placement, type locality and distribution.
• Seriously Fish: Pterophyllum scalare species profile: aquarium size, water values, diet, behaviour, sexing and breeding.
• OATA: How to look after American cichlids: UK trade-body care sheet for the wider group, including water, stocking, feeding and maintenance.
• RSPCA: Fish environment: filtration and the nitrogen cycle.
• RSPCA: Fish health and welfare: visible health signs and water-quality-first checks.
• Kasiri, Farahi and Sudagar (2012), growth and reproductive performance by feed type in freshwater angelfish: controlled feeding study.
• Tropical Fish Co freshwater angelfish care guide: our tank, water, social and health planning for Pterophyllum scalare.
• Tropical Fish Co delivery and Live Arrival Guarantee policy: packing, courier and arrival steps.