Rio Nanay Angelfish (Pterophyllum scalare)

Rio Nanay Angelfish (Pterophyllum scalare) is a Peruvian locality form of the freshwater angelfish, valued for its tall wild-type outline, vertical bars and the spotted detail often associated with Nanay fish. “Rio Nanay” describes the locality form; it is not a third word in the scientific name. The accepted species is Pterophyllum scalare.

This is a large, intelligent South American cichlid rather than a small ornamental fish for a short tank. Juveniles may look delicate and sociable, but adults can reach about 15 cm total length with much greater vertical fin height, form pairs and defend a spawning site. A successful aquarium therefore needs height, at least a 100 cm length, mature filtration, stable warm water and a plan for adult social behaviour.

Rio Nanay Angelfish care at a glance

These are working aquarium targets, not instructions to swing the chemistry between limits. Stability matters more than chasing a single “perfect” number. Compare measured source water with the water matcher, and calculate the actual filled volume with the tank-volume tool after allowing for substrate and hardscape.

What “Rio Nanay” means

The Rio Nanay is a tributary system near Iquitos in the Peruvian Amazon. FishBase occurrence data includes P. scalare records from streams entering the Rio Nanay and from the Nanay drainage near Iquitos. This supports the locality association without turning “rio nanay” into a subspecies name.

Locality forms matter because populations can differ in pattern, body proportions and aquarium history. Nanay-type fish are often described with a tall wild-type body, strong bars and brown or reddish spotting. Expression varies with age, lighting, mood and lineage. A juvenile may not yet show the full adult pattern, and a photograph cannot prove collection locality or generation. Preserve the locality name accurately, but avoid claims such as wild-caught, F1 or “pure line” unless documentary provenance accompanies the stock.

Rio Nanay scalare is not true Altum Angelfish

True Altum Angelfish is Pterophyllum altum, a different accepted species. The hobby names “Peruvian Altum” and “Peru Altum” are sometimes used for tall Rio Nanay P. scalare, but the names can mislead. Customers comparing the two should use the scientific name and locality, not body height alone. Our Altum Angelfish guide explains the distinction in more detail.

Natural range and habitat

Eschmeyer's Catalog of Fishes accepts Pterophyllum scalare as a valid species distributed through the Amazon basin, including Peru. FishBase describes adults in swamps and flooded areas with dense aquatic or river-edge vegetation, in clear or silty water. The deep, laterally compressed body and long fins suit slow, structured habitat better than exposed fast current.

An aquarium translation should prioritise height, calm zones and vertical structure. Tall plants, upright wood and shaded margins help create cover without filling every swimming lane. The fish needs room to turn cleanly and move as a group. A blackwater appearance can be created with tannin-stained water and leaf litter, but colour is optional; water quality, oxygen and stability are not.

Adult size and aquarium dimensions

FishBase reports a maximum around 15 cm total length and recommends a minimum aquarium length of 100 cm. The apparent size is greater because the dorsal, anal and pelvic fins extend vertically. A tank can meet a litre figure and still be unsuitable if it is too short or shallow.

Around 150 litres can serve as a practical lower planning point for a compatible adult pair when the aquarium is at least 100 cm long and sufficiently tall. A juvenile group needs more water and more escape space as individuals mature. For five or more fish, a substantially larger 180-250 litre aquarium is easier to manage, and larger still is preferable when tank mates are included.

Setting up the aquarium

Filtration and flow

Use mature biological filtration with good oxygen exchange and gentle to moderate circulation. Avoid a narrow high-speed jet across the main swimming area. An external filter, large internal filter or carefully arranged sponge filtration can work if it handles the waste load. Protect intakes when very small juveniles or fry are present.

Plants and hardscape

Use vertical wood, broad-leaved plants and open lanes. Angelfish often choose a broad leaf, slate or filter surface for spawning, so stable upright surfaces have practical value. Anchor hardscape securely and leave enough room behind it for cleaning. Dense cover at the back and sides can reduce line-of-sight pressure while the centre remains open.

Substrate and lighting

Fine sand or smooth small gravel is suitable. Darker substrate and moderate lighting often show the bars well, but the fish should always have shaded cover. Avoid sharp decor that can catch long fins. Complete the nitrogen cycle before arrival; the cycle tracker helps record ammonia, nitrite and nitrate rather than relying on elapsed time alone.

1. Choose a tall aquarium at least 100 cm long.
2. Install mature filtration and create gentle, oxygenated flow.
3. Add vertical cover while preserving clear turning and feeding space.
4. Cycle fully and prove ammonia and nitrite remain at zero.
5. Measure pH, hardness and temperature over several days.
6. Prepare a divider or second cycled aquarium before an adult pair forms.

Water parameters and maintenance

FishBase lists 24-30°C, pH 6.0-8.0 and 5-13 dH for the species. For routine care of this stock, 25-28°C, pH 6.0-7.5 and 5-12 dGH form a conservative working range. Ask how the fish is currently held and acclimate to the destination rather than forcing a sudden change towards an imagined blackwater ideal.

Soft, warm water can lose buffering capacity, so test carbonate hardness as well as pH. Prepare replacement water in advance and match temperature closely. Weekly partial changes are a sensible starting rhythm, adjusted to measured nitrate, feeding and stocking. Never replace all filter media at once.

Feeding Rio Nanay Angelfish

A recent Rio Nanay basin study reported phytoplankton, detritus and zooplankton in P. scalare stomach contents, including juvenile consumption of Cyclops. In the aquarium, use a balanced high-quality cichlid pellet or flake as a measured staple and rotate small frozen or live foods such as cyclops, daphnia, brine shrimp, mysis and suitable insect-larva foods.

Feed adults once or twice daily in portions consumed promptly. Juveniles can receive smaller meals more often when filtration and maintenance support growth. Spread food so quieter fish eat; the tallest or boldest individual should not take every particle. Avoid mammal meat, oversized sticks and repeated heavy bloodworm meals.

Group behaviour and pair formation

FishBase recommends groups of five or more for aquarium keeping, but this advice must be combined with adult cichlid behaviour. Juveniles can benefit from group security and social choice. As they mature, a pair may form and defend a territory. The rest of the group then needs enough room to leave that zone.

Do not assume that two purchased juveniles will become a compatible pair. Sexing before maturity is unreliable, and a pair bond can change. Watch for equal feeding, normal colour and free access to cover. A fish pinned behind a filter, at the surface or in a corner is not merely “subordinate”; it needs space, a divider or removal.

Tank mates and predation risk

Rio Nanay Angelfish can share a carefully chosen community outside breeding, but “peaceful” is conditional. Companions must tolerate warm, moderately soft water, be too large to swallow and avoid fin-nipping. Larger peaceful tetras, calm medium rasboras, compatible Corydoras and Bristlenose-type plecos may work in a sufficiently large aquarium, but every species must be checked individually.

Avoid Tiger Barbs and other habitual fin-nippers. Very small tetras or shrimp may be eaten by adult Angelfish. Large aggressive cichlids can intimidate or injure them. Gouramis and other tall territorial fish may compete visually and socially. Use our Angelfish tank-mates guide and tank-mates tool as starting checks, then judge the actual aquarium footprint and fish behaviour.

Breeding behaviour

Pterophyllum scalare is a substrate-brooding cichlid with biparental care. A pair cleans a vertical or angled surface, lays adhesive eggs and guards the brood. Research also describes serial monogamy rather than assuming every bond is permanent. Pair aggression can rise sharply around spawning.

Broad plant leaves, slate or spawning cones provide a suitable surface. Stable warm water, varied feeding and privacy support natural behaviour, but spawning should not be forced through sudden water changes. If a community pair defends half the aquarium, move the pair or other fish before injuries occur.

Parents may fan and move embryos or larvae. Captive strains sometimes eat early broods, particularly when disturbed. Avoid tapping glass, moving the spawning surface or repeatedly shining lights at eggs. Fry need microscopic first foods followed by freshly hatched baby brine shrimp as they become free-swimming; protect filter intakes.

Health and quarantine

A healthy Angelfish holds its fins open, feeds readily, breathes evenly and maintains a full but not swollen body. Warning signs include clamped fins, rapid breathing, a hollow belly, white spots, stringy waste, repeated scratching, dark isolation or a fish driven away from every feeding area.

Test water before medication. Ammonia, nitrite, overheating, low oxygen and social stress can imitate disease or make it worse. Quarantine new fish in matched warm water with vertical cover. Observe appetite and waste, and use separate equipment. Do not combine fish from different sources immediately because a healthy-looking carrier can expose an established group.

Arrival and acclimation

Before dispatch day, complete water tests, dim the lights and make sure every new fish has vertical cover. Follow the supplied method rather than applying an automatic long drip to every opened bag; ammonia risk changes after transport water is exposed to air. The acclimation timer can help keep the process organised.

Do not add bag water to the aquarium. Release the fish gently, leave lighting low and offer only a small meal after it has settled. Check that both current size options can use the planned cover without being drawn into filter intakes. Our live-fish delivery page explains packing, evidence requirements and the Live Arrival Guarantee.

Choosing this locality form

Choose Rio Nanay Angelfish when you want a natural-looking P. scalare with a documented Peruvian locality association, and when the aquarium can support adult size and pair behaviour. Do not choose it only because a small juvenile fits the current tank. Compare the general Angelfish care guide, the Manacapuru Angelfish listing and the wider Angelfish collection before deciding which form suits the display.

• Good fit: tall 100 cm+ mature aquarium, stable warm water, measured feeding and space to manage a forming pair.
• Pause first: uncertain water chemistry, a newly cycled tank or no quarantine/backup accommodation.
• Poor fit: short nano aquarium, tiny tank mates, habitual fin-nippers or an overcrowded cichlid community.

WELCOME10 may provide 10% off an eligible first order; checkout confirms whether the offer applies. Current size and availability are shown by the live variant selector rather than hard-coded into this care guide.

Frequently asked questions

What is the correct scientific name for Rio Nanay Angelfish?

The accepted species name is Pterophyllum scalare. Rio Nanay is a Peruvian locality form and should not be written as a third taxonomic word or treated as a separate accepted species on this listing.

Is Rio Nanay Angelfish a true Altum?

No. True Altum Angelfish is Pterophyllum altum. “Peruvian Altum” or “Peru Altum” can be a trade nickname for tall Rio Nanay P. scalare, but it does not change the scientific identity.

Are these fish wild-caught or F1?

This listing does not claim wild-caught or F1 provenance unless that information is explicitly attached to the current stock. The locality-form name and appearance alone cannot prove collection history or generation.

How large do Rio Nanay Angelfish grow?

FishBase reports a maximum around 15 cm total length for P. scalare, with long fins making the fish much taller. Plan for an adult from the start, not the juvenile dispatch size.

What tank size do they need?

Use a tall aquarium at least 100 cm long. Around 150 litres is a practical lower plan for a compatible pair; a group of five or more needs roughly 180-250 litres or more, especially with tank mates.

What water parameters suit Rio Nanay Angelfish?

A practical routine target is 25-28°C, pH 6.0-7.5 and 5-12 dGH, with ammonia and nitrite at zero. FishBase gives a broader species range of 24-30°C, pH 6.0-8.0 and 5-13 dH.

Can they live with Neon Tetras?

Very small tetras can be eaten by adult Angelfish. Choose companions that are warm-water compatible, peaceful, too large to swallow and not inclined to nip long fins.

Should Rio Nanay Angelfish be kept alone, as a pair or in a group?

Juveniles are often best raised in a group of five or more where space permits. Adults may form a territorial pair, so a large footprint and a separation plan are essential. Two random juveniles are not guaranteed to become compatible.

Sources and evidence

• Eschmeyer's Catalog of Fishes for accepted identity and Amazon-basin distribution.
• FishBase species summary for size, habitat, water range and aquarium length guidance.
• FishBase occurrence records for Rio Nanay drainage records near Iquitos.
• Embryonic and larval development in freshwater angelfish for substrate brooding and biparental care.
• Rio Nanay ornamental-fish diet study for locality-specific feeding evidence.

Care guidance combines cited species evidence with conservative aquarium planning for the stock offered here. Volume recommendations are practical minimum planning guidance, not measurements from the wild. Observe the individual fish and adjust stocking before conflict develops.