Altum Angelfish Care Guide: Tank Height, Soft Water & Group Size

Q: How is Pterophyllum altum different from a regular angelfish?

The common aquarium angelfish (Pterophyllum scalare, covered generally in our angelfish skin peeling guide) and the altum angelfish (Pterophyllum altum) are related but distinct species, and altum is considerably more demanding on essentially every axis. Altums are taller-bodied — adults can reach 12-14 inches in height including fins, compared to roughly 10-12 inches for large P. scalare — and they're far more sensitive to water chemistry, requiring softer, more acidic water than the common angelfish typically needs. Altums are also frequently wild-caught or only a generation or two removed from wild stock, unlike the heavily domesticated P. scalare varieties common in the trade, which contributes to their reputation for being less forgiving of suboptimal conditions.

Q: Why does altum angelfish care emphasize tank height so much?

Because of the species' body shape: altum angelfish are unusually tall relative to their body length, with adults reaching 12-14 inches in height including their long dorsal and anal fin extensions, while their body length is closer to 7 inches. A tank that's adequate in length and width but only 18-20 inches tall — common for many standard aquarium dimensions — physically doesn't give an adult altum room to move naturally, and tall fish in tanks that are too short for them are at higher risk of fin damage and stress from constantly brushing the substrate or water surface. 30+ inches of water height is generally recommended as a minimum for adults, which rules out many standard tank shapes and often means choosing a tank specifically for its height rather than its footprint or volume alone.

Q: Can altum angelfish be kept in regular community tank water parameters?

Not well, long-term. Altum angelfish come from the soft, acidic blackwater of the Orinoco and Rio Negro basins, and do best in water that's considerably softer and more acidic (commonly cited around pH 4.5-6.0) than the more moderate parameters (pH 6.5-7.5) that suit common angelfish and many community fish. They're also generally kept warmer (82-86°F) than many community tanks are set up for. Altums can survive outside this range for periods, similar to how many fish tolerate suboptimal conditions without thriving, but their reputation for being 'difficult' compared to common angelfish is substantially explained by keepers attempting to house them in parameters suited to P. scalare or general community fish rather than altum's actual blackwater origins.

Q: Do altum angelfish need to be kept in groups?

Yes, generally — altum angelfish are considered a more social, group-oriented species than the common angelfish is often treated as, and are frequently recommended to be kept in groups of 5 or more in a sufficiently large and tall tank, both for the fish's wellbeing and because group dynamics can reduce the targeted aggression that might otherwise focus on a single individual. This is a different consideration from the stress bars discussed in our angelfish skin peeling guide — group housing doesn't prevent normal stress-bar color changes (which are temporary and benign), but adequate group size and tank space can reduce the frequency of genuinely stressful interactions that might contribute to other issues.

By Hektor Jorgo Published May 30, 2023 Updated June 13, 2026 5 min read

A tall-bodied altum angelfish swimming among driftwood and leaf litter in a blackwater-style aquarium

Quick Facts

Scientific Name: Pterophyllum altum
Common Names: Altum angelfish, deep angelfish, Orinoco angelfish
Native Range: Orinoco and upper Rio Negro river basins, South America — soft, acidic blackwater
Care Level: Advanced — sensitive to water chemistry, requires an unusually tall tank
Minimum Tank Size: Tank height of 30+ inches (75+ cm); 75+ gallons for a small group of adults
Diet: Omnivore — high-quality flake/pellet plus live or frozen foods
Max Size: Body height up to 12-14 inches with fins; body length around 7 inches
Water Parameters: Soft, acidic, warm — pH 4.5-6.0, temperature 82-86°F (much more demanding than common angelfish)

The altum angelfish (Pterophyllum altum) is often grouped together with the common angelfish in casual conversation, but the two species diverge significantly in their needs — taller, more sensitive to water chemistry, and generally considered an advanced-keeper fish rather than the community-tank staple the common angelfish has become.

Appearance and Natural Range

Altum angelfish share the same general silhouette as common angelfish — a tall, laterally compressed, roughly diamond-shaped body with long, trailing dorsal and anal fins — but taken to a more extreme degree. Adult altums can reach 12-14 inches in total height including fins, considerably taller relative to body length than Pterophyllum scalare.

The species is native to the Orinoco and upper Rio Negro river basins in South America, an environment characterized by soft, acidic, tannin-stained "blackwater" — water colored by dissolved organic compounds from decaying leaf litter, with very low mineral content and pH often well below neutral.

Tank Requirements

Tank Size

Tank height is the defining requirement for this species: 30+ inches (75+ cm) of water height is generally recommended as a minimum for adults, given their extreme body height. A tank that's spacious in footprint but short — many standard rectangular tanks are 18-20 inches tall — doesn't provide adequate vertical space for an adult altum, and can contribute to fin damage and stress. For a group of adults (5+, given their social nature), 75+ gallons in a tall format is a realistic minimum.

Aquascaping

A blackwater biotope-style setup suits altum angelfish well and reflects their natural habitat: driftwood, leaf litter (such as Indian almond leaves, which also release tannins), and dim lighting. Dense planting isn't required — altums in the wild are often found among submerged tree roots and driftwood rather than dense vegetation — but tall, vertical hardscape elements complement the fish's body shape and natural behavior.

Water Parameters

Parameter	Target Range
Temperature	82-86°F (28-30°C)
pH	4.5-6.0
Ammonia / Nitrite	0 ppm
Nitrate	<10-20 ppm
Water hardness	Very soft (1-4 dGH)

These parameters are notably more extreme than those for common angelfish or most community fish — both warmer and considerably softer/more acidic. This is the area where altum care most often goes wrong: a tank set up with standard community parameters (moderate hardness, pH 7+, 76-78°F) is a meaningfully different environment than what this species evolved for.

Diet and Feeding

Altum angelfish are omnivores and accept a similar range of foods to common angelfish:

High-quality flake or pellet food as a staple
Live or frozen foods (bloodworms, daphnia, brine shrimp) for variety and conditioning
As with many wild-caught or near-wild-type fish, newly acquired altums may take time to adjust to prepared foods, and live or frozen foods can help during this adjustment period

Tank Mates and Compatibility

Altum angelfish are generally recommended to be kept:

In groups of 5 or more — reflecting their social nature and helping distribute any territorial interactions across more individuals rather than concentrating on one fish
With other soft-water, blackwater-tolerant species — tank mates need to handle the same low pH and soft water altums require, which rules out many standard community fish
In a tall tank that accommodates both the altums' body shape and any tank mates' needs

Given the specialized water chemistry requirements, altum tank mates are typically chosen from other soft-water South American species rather than general community fish lists.

Altum vs. Standard Angelfish: Key Differences

Aspect	Common Angelfish (P. scalare)	Altum Angelfish (P. altum)
Body height (adult)	~10-12 inches with fins	~12-14 inches with fins
Water pH	6.5-7.5	4.5-6.0
Temperature	76-82°F	82-86°F
Origin	Heavily domesticated, many varieties	Often wild-caught or near-wild
Tank height needed	Moderate	30+ inches minimum
Care level	Beginner-to-intermediate	Advanced

A keeper experienced with common angelfish shouldn't assume that experience transfers directly to altums — the water chemistry and tank height requirements are different enough that altum is generally considered its own undertaking, not a "bigger version" of the same fish.

Common Health Issues

Stress from inappropriate water chemistry — given altum's narrow preferred range, fish kept in standard community parameters are at elevated risk of chronic stress-related issues over time
Stress bars and skin issues — the same general considerations covered in our angelfish skin peeling guide apply to altums, with the added factor that a fish already stressed by suboptimal water chemistry may be more susceptible to secondary issues
Fin damage from inadequate tank height — a tall fish in a too-short tank is more prone to fin damage from contact with the substrate or water surface

Quick Setup Checklist

Tank: 30+ inches of water height minimum, 75+ gallons for a group of adults
Blackwater-style setup: driftwood, leaf litter, dim lighting
Water: 82-86°F, pH 4.5-6.0, very soft (1-4 dGH)
Keep in groups of 5+ where space allows
Diet: quality flake/pellet plus live/frozen foods; allow time for newly acquired fish to adjust
Choose tank mates from soft-water, blackwater-tolerant species
Don't assume common angelfish experience transfers directly — altum is an advanced-keeper undertaking

Frequently Asked Questions

How is Pterophyllum altum different from a regular angelfish?

The common aquarium angelfish (Pterophyllum scalare, covered generally in our angelfish skin peeling guide) and the altum angelfish (Pterophyllum altum) are related but distinct species, and altum is considerably more demanding on essentially every axis. Altums are taller-bodied — adults can reach 12-14 inches in height including fins, compared to roughly 10-12 inches for large P. scalare — and they're far more sensitive to water chemistry, requiring softer, more acidic water than the common angelfish typically needs. Altums are also frequently wild-caught or only a generation or two removed from wild stock, unlike the heavily domesticated P. scalare varieties common in the trade, which contributes to their reputation for being less forgiving of suboptimal conditions.

Why does altum angelfish care emphasize tank height so much?

Because of the species' body shape: altum angelfish are unusually tall relative to their body length, with adults reaching 12-14 inches in height including their long dorsal and anal fin extensions, while their body length is closer to 7 inches. A tank that's adequate in length and width but only 18-20 inches tall — common for many standard aquarium dimensions — physically doesn't give an adult altum room to move naturally, and tall fish in tanks that are too short for them are at higher risk of fin damage and stress from constantly brushing the substrate or water surface. 30+ inches of water height is generally recommended as a minimum for adults, which rules out many standard tank shapes and often means choosing a tank specifically for its height rather than its footprint or volume alone.

Can altum angelfish be kept in regular community tank water parameters?

Not well, long-term. Altum angelfish come from the soft, acidic blackwater of the Orinoco and Rio Negro basins, and do best in water that's considerably softer and more acidic (commonly cited around pH 4.5-6.0) than the more moderate parameters (pH 6.5-7.5) that suit common angelfish and many community fish. They're also generally kept warmer (82-86°F) than many community tanks are set up for. Altums can survive outside this range for periods, similar to how many fish tolerate suboptimal conditions without thriving, but their reputation for being 'difficult' compared to common angelfish is substantially explained by keepers attempting to house them in parameters suited to P. scalare or general community fish rather than altum's actual blackwater origins.

Do altum angelfish need to be kept in groups?

Yes, generally — altum angelfish are considered a more social, group-oriented species than the common angelfish is often treated as, and are frequently recommended to be kept in groups of 5 or more in a sufficiently large and tall tank, both for the fish's wellbeing and because group dynamics can reduce the targeted aggression that might otherwise focus on a single individual. This is a different consideration from the stress bars discussed in our angelfish skin peeling guide — group housing doesn't prevent normal stress-bar color changes (which are temporary and benign), but adequate group size and tank space can reduce the frequency of genuinely stressful interactions that might contribute to other issues.

Sources & Further Reading

About the Author: Hektor Jorgo

Co-Founder & Marine Biologist

Hektor is a co-founder of Sea Life Planet and has kept reef and freshwater aquariums for over 15 years. He holds a background in marine biology and focuses on species care accuracy, water chemistry, and tank husbandry.