Altum Angelfish Care Guide (Pterophyllum altum)

Altum angelfish (Pterophyllum altum) are the largest of the three recognized freshwater angelfish species and are distinguished by their exceptionally tall, laterally compressed bodies and prominent vertical bands. Adults can reach approximately 15–18 cm (6–7 inches) in standard length and 35–40 cm (14–16 inches) in total height from the tip of the dorsal fin to the tip of the anal fin.

True altums can also be identified by their characteristic steep forehead and pronounced notch above the snout, which helps distinguish them from the closely related Pterophyllum scalare.

Origin & Natural Habitat

Altum angelfish are native to northern South America, where they occur primarily within the upper Orinoco River basin and upper Rio Negro drainage. Important collection localities include the Rio Atabapo and Rio Inírida systems of Colombia and Venezuela.

Their natural habitats include highly acidic, exceptionally soft blackwater rivers with slow currents and extensive submerged structure. Fallen tree trunks, branches, roots and other woody debris provide cover, feeding areas and territories throughout these flooded river systems.

Research highlight: Observations from Colombian blackwater habitats found altums consistently sheltering under cover rather than remaining in open water. Juveniles were observed in shallow areas of approximately 50–80 cm, while larger adults occurred at considerably greater depths. Altums were frequently found among submerged branches, tree trunks, roots and even rock formations.

Altum Angelfish Care

Altum angelfish are best suited to intermediate or advanced aquarists because they require a large aquarium, consistently high water quality and careful management of water chemistry. Wild-caught altums can be particularly demanding because they are sensitive to collection, transportation, acclimation and repeated changes in water conditions, which can leave newly imported fish stressed and in poor condition.

Captive-bred altums are generally easier to acclimate because they may already be accustomed to aquarium conditions and prepared foods. When purchasing wild-caught specimens, it is especially important to determine the water parameters in which the fish are currently being maintained rather than immediately attempting to recreate the extremely acidic conditions of their natural habitat.

Research highlight: Wild altum angelfish may experience a gradual increase in pH throughout the export process, from values as low as approximately 4.0 in their native blackwater habitat to around 6.0–7.5 at aquarium stores. Caution should be exercised when placing newly imported altums directly into extremely acidic water, as this can create another sudden change in water chemistry and cause additional stress. Allow newly imported fish to recover and make any transition toward natural blackwater conditions gradually.

Tank Size

A tall aquarium of at least 125 gallons is recommended for adult altum angelfish, with larger aquariums preferred when maintaining groups or additional tank mates. Recommended minimum aquarium dimensions are approximately 200×60×60 cm (79×24×24 inches) for a group of ten altums, not accounting for substrate depth.

Aquarium height is especially important because mature altums can reach approximately 35–40 cm (14–16 inches) from the tip of the dorsal fin to the tip of the anal fin. Adequate aquarium height allows the dorsal, anal and elongated pelvic fins to remain naturally extended while swimming, reducing the risk of bending, deformation or repeated contact with the substrate and aquarium surfaces.

Substrate depth should also be considered when determining usable aquarium height because a 60 cm-high aquarium may provide only approximately 50–55 cm of actual water-column height once the substrate and upper waterline are accounted for.

Water Parameters

Altum angelfish naturally inhabit exceptionally soft, acidic water and should not be maintained in hard, alkaline conditions. Recommended aquarium parameters include:

Temperature: 80.6–88°F (27–31°C)
pH Range: 4.8–6.2
General Hardness (GH): 1–5 dGH

Maintaining consistently clean and stable water parameters is particularly important for altum angelfish. Poor water quality and accumulating organic waste can cause severe stress, increase the risk of bacterial infections such as fin rot and, in prolonged or severe cases, contribute to mortality.

Ammonia and nitrite should remain at 0 ppm in an established aquarium, while nitrate and accumulating organic waste should be kept low through regular water changes, appropriate stocking levels, substrate cleaning and the removal of uneaten food and waste. Live aquatic plants or algae can also contribute to nitrate uptake.

Aquarists with hard source water may need to dilute their tap water with reverse-osmosis or demineralized water to achieve sufficiently low mineral concentrations.

Aquarium Setup

Altum angelfish benefit from a tall aquarium containing submerged branches, driftwood, floating plants and tall aquatic plants. These features more closely resemble their natural habitat while dividing the aquarium into separate territories and breaking direct lines of sight between competing fish.

Newly imported wild-caught altums may become highly skittish and occasionally dart when frightened. Subdued lighting, floating plants and dark backgrounds can help create a calmer environment during acclimation. Sharp decorations or objects capable of causing injury should be avoided.

Diet & Feeding

Altum angelfish are opportunistic predators that consume small fish, aquatic and terrestrial insects, insect larvae, worms, crustaceans and other small invertebrates. Their terminal mouth allows them to capture prey throughout the water column and near the surface, where insects and other terrestrial organisms may enter the water.

In captivity, altums should receive a varied, protein-rich diet containing high-quality pellets or flakes supplemented with frozen or live foods. Prepared foods formulated for discus or other large cichlids can also provide a nutritionally balanced diet.

Suitable supplementary frozen or live foods include:

• Artemia
• Daphnia
• Bloodworms
• Mosquito larvae
• Glassworms
• Krill
• Mysis shrimp

Feed adult altums approximately two to three times per day, offering only what they can consume within a few minutes. Young, actively growing altums may benefit from several smaller feedings throughout the day to support healthy growth and body development. Regular feeding of protein-rich foods is especially important during growth and when conditioning mature fish for breeding.

Wild-caught altums may initially be reluctant to accept commercially prepared foods. Live or frozen foods are best used during acclimation before gradually introducing pellets or flakes. Healthy altums generally develop a strong feeding response once established.

Altum Angelfish Tank Mates

Altum angelfish are social cichlids that are typically maintained in groups, particularly while young. Juveniles establish a social hierarchy as they mature, but territorial aggression can increase once breeding pairs begin to form. Established pairs may occupy substantial portions of an aquarium and aggressively exclude other altums from their territory.

Aquarium layout is particularly important when keeping groups. Driftwood, plants and other tall decor can break lines of sight and provide areas for fish to retreat. If a mature pair begins monopolizing the aquarium, the remaining fish may need to be separated.

Suitable tank mates should be peaceful, large enough to avoid being swallowed and capable of tolerating the warm, soft water preferred by altums. Very small fish may be consumed, while aggressive species, persistent fin-nippers and extremely active fish can cause unnecessary stress.

Discus are commonly kept with altums because both can thrive under similar warm, soft-water conditions. Larger tetras, appropriately sized corydoras, peaceful plecos and selected South American cichlids may also be suitable when their temperature requirements and temperament are compatible.

Compatible Tank Mates

Note: Individual temperament can vary; species that coexist peacefully in one aquarium may not do so in another. Monitor newly introduced fish for excessive fin-nipping, fin damage, persistent aggression, or signs of stress, and separate incompatible fish when necessary.

Male vs Female Differences

Male and female altum angelfish exhibit very few reliable sexually dimorphic characteristics, making juveniles and non-breeding adults extremely difficult to sex.

Mature males may develop a somewhat larger body and more pronounced forehead or nuchal hump, although these characteristics are not dependable enough to determine sex on their own.

The most reliable differences become visible during breeding condition. Males typically develop a smaller, narrower and more pointed genital papilla located in between their ventral and anal fins, while females develop a larger, blunter ovipositor used to deposit eggs.

Altum Angelfish Breeding Guide

True wild-caught altum angelfish are particularly challenging to reproduce successfully in captivity. In their natural habitat, seasonal rainfall raises water levels substantially and floods surrounding forests, providing considerably more territory and potential spawning sites. During field observations in Colombia, water levels in the Rio Inírida were reported to rise by approximately 8 meters (26 feet) during the rainy season, while the surrounding plains of the Rio Atabapo can become extensively flooded.

To mimic these conditions as closely as possible, successfully breeding altums generally requires a large aquarium with exceptionally soft, acidic water, excellent water quality and sufficient space for compatible pairs to establish territories. An aquarium approaching 200 gallons is preferable when maintaining a breeding group, and having a second aquarium available is strongly recommended so that competing fish can be relocated once a pair becomes established.

Conditioning Altum Angelfish for Breeding

Altum angelfish require very soft, acidic water for breeding, which can be achieved using rainwater or demineralized water when necessary. Recommended breeding conditions include:

• Temperature: 82.5–84°F (28–29°C)
• pH Range: 4.5–5.0
• General Hardness (GH): Below 1.5 dGH (25 ppm CaCO₃)

Tannin-stained blackwater conditions can also be recreated using peat filtration, driftwood, almond leaves or other suitable sources of tannins. This can contribute to a lower pH in already soft, weakly buffered water while recreating characteristics of the natural blackwater environments in which altums reproduce.

The aquarium should contain submerged roots, broad-leaved plants, branches or other vertical surfaces that can be used for spawning. The aquarium layout should also create several separate territories and break direct lines of sight between competing fish. Gentle water circulation is preferred around potential spawning areas.

Strict aquarium maintenance and water quality are paramount throughout conditioning and breeding. Perform a weekly water change of approximately 50%, supplemented with one or two smaller 10% water changes throughout the week. A bare bottom or thin layer of sand, preferably less than 1 cm deep, allows food, excrement and organic waste to be easily siphoned.

Several mature altums can initially be maintained together and allowed to establish their own social hierarchy and breeding pairs. It may take several weeks or considerably longer for a compatible male and female to establish a territory and form a stable pair.

As the altum angelfish display breeding behavior, their dorsal and anal fins may develop an intense dark-red coloration. Paired individuals may also display stronger territorial behavior, position themselves face-to-face and repeatedly inspect or clean potential spawning surfaces. The appearance of intense red coloration should be viewed as a sign of breeding behavior rather than a guarantee that spawning will immediately occur.

During this period, condition the altum angelfish with frequent feedings of high-quality, protein-rich live or frozen foods such as mosquito larvae, mysis shrimp and Artemia.

Once a compatible pair becomes established, competing altums should be removed if they continually enter the pair’s territory or provoke persistent aggression. Do not separate the established male and female because both parents can actively participate in protecting and rearing their offspring.

Research highlight: In Sven Fornbäck’s documented 1994 breeding account, an established discus pair was temporarily introduced after his altum pair repeatedly failed to spawn. The discus spawned within three days, after which the altums intensified their spawning-site preparation and eventually produced their own clutch. Fornbäck believed the reproductive behavior of the discus helped stimulate the altum pair, although this observation represents one successful breeding method rather than a requirement for spawning.

Spawning & Egg Care

Before spawning, the female and male may investigate and clean several potential sites. Broad plant leaves, submerged roots, branches and smooth artificial spawning surfaces can all be used. Smooth spawning surfaces may improve egg survival because cracks and irregularities in natural wood can harbor microorganisms that are difficult for the parents to remove.

During spawning, the female deposits adhesive eggs in organized rows across the selected surface while the male follows to fertilize them. A mature female can produce several hundred eggs during a single clutch, with documented successful spawnings producing approximately 600 eggs over the course of several hours.

Once eggs are visibly present, begin daily water changes of approximately 10%. These small water changes help maintain exceptionally clean conditions, replenish dissolved oxygen and reduce the accumulation of organic waste that can contribute to fungal growth. Carefully siphon the substrate or bare bottom during each water change to remove any remaining food, organic waste and debris without disturbing the eggs or breeding pair.

Both parents can participate in brood care by guarding and continuously fanning the clutch to maintain water movement across the developing eggs. Unfertilized or nonviable eggs generally turn white and are removed by the parents with their mouths before fungal growth can spread to surrounding viable eggs.

At approximately 30°C (86°F), the larvae can begin emerging around 60 hours after fertilization. After hatching, the larvae remain attached while continuing to consume their yolk-sac reserves. The parents may collect newly hatched larvae in their mouths and transfer them to another clean and protected surface.

During the following several days, both parents continue to guard the larvae. As individual fry begin attempting to swim away, the adults may retrieve them with their mouths and return them to the nesting area.

Raising Altum Angelfish Fry

The fry generally become fully free-swimming approximately six to seven days after spawning. They continue relying on their yolk-sac reserves during the earliest stage of development and should not be fed prematurely.

Once most of the yolk sac has been absorbed and the fry begin actively feeding, offer small meals approximately four times per day. Freshly hatched Artemia nauplii make an excellent first food and can be introduced as soon as the fry are large enough to consume them.

During the first 30 days, continue daily water changes of approximately 10% and siphon accumulated waste to maintain water quality and reduce fry mortality.

As the juveniles grow, their diet can gradually expand to include daphnia, baby brine shrimp, mosquito larvae and other appropriately sized live or frozen foods. High-quality prepared foods can also be introduced gradually once the young fish are large enough and readily accept them.

After approximately 30 days, the young altums can begin a gradual transition toward the water conditions in which they will ultimately be maintained. This can be accomplished by performing approximately 10% water changes each day for the following seven days while progressively introducing the intended source water. Any increase in mineral content or pH should occur gradually, and altums should continue to be maintained in relatively soft, acidic water rather than being abruptly transferred into hard, alkaline conditions.

Note: Altum angelfish are extremely difficult to breed consistently, and no universal method guarantees a successful spawn. Success often requires considerable experience, careful observation and repeated attempts.

Species Overview

Pterophyllum altum was formally described by French zoologist Jacques Pellegrin in 1903. Pellegrin’s original description appeared in Bulletin du Muséum d’Histoire Naturelle and was based on specimens originating from the upper Orinoco region.

The genus Pterophyllum currently contains three commonly recognized species: P. altum, P. scalare and P. leopoldi. A major taxonomic review published by Smithsonian ichthyologist Leonard P. Schultz in 1967 examined wild specimens and type material to clarify morphological differences within the genus.

Altums entering the aquarium trade are often identified by geographic locality, including Rio Atabapo, Rio Inírida, Rio Orinoco and related drainage populations. These locality names can be useful when discussing wild collection origin or established captive breeding lines but should not automatically be interpreted as formally recognized subspecies.

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ForAquarium species guides combine scientific literature and established taxonomic references with years of aquarium-keeping experience. Information is periodically reviewed and updated as new research becomes available.