How To Identify A True Altum Angelfish – The Complete Expert Guide
To identify a true altum angelfish (Pterophyllum altum), look for a distinct supraorbital notch above the snout, exceptionally tall vertical fins, and a dorsal ray count between 27 and 30, typical of the Orinoco basin.
The Pterophyllum altum, commonly known as the Orinoco Altum, is often considered the “holy grail” of the freshwater aquarium hobby. Many enthusiasts spend years searching for these majestic giants, only to be disappointed by mislabeled specimens in local fish stores.
In my experience, the confusion usually stems from the similarity between the true Altum and certain wild-type Pterophyllum scalare varieties. After keeping various species of these “Kings of the Aquarium” for over a decade, I have learned that the devil is truly in the details.
Understanding how to identify a true altum angelfish requires a keen eye for anatomy and a bit of knowledge regarding their natural origins. This guide will walk you through the specific biological markers that separate the true legend from its common cousins.
Pro Tip: When shopping for Altums, always ask the seller for the specific collection point. True Altums are almost exclusively exported from the Rio Orinoco and Rio Atabapo regions, whereas “Peru Altums” are actually a variety of Pterophyllum scalare.
The Anatomy of a Legend: How to Identify a True Altum Angelfish
The most reliable way to distinguish a true Altum from a standard angelfish is by examining the head shape. True Altums possess a very specific “stop” or indentation located just above the eyes and before the dorsal fin begins.
This feature is scientifically referred to as a supraorbital notch or a pre-dorsal indentation. This gives the fish a “turned-up” snout appearance that is much more pronounced than in any other species in the genus.
If the profile of the fish from the mouth to the dorsal fin is relatively straight or only slightly curved, you are likely looking at a Pterophyllum scalare. A true Altum will always have that sharp, distinctive “break” in its silhouette.
Counting the Dorsal Rays
If you want to be 100% certain of your identification, you may need to get a bit technical and look at the fin rays. The dorsal ray count is a definitive taxonomic marker used by ichthyologists to classify these fish.
True Altums typically have 27 to 30 soft rays in their dorsal fin, which is significantly higher than the 23 to 26 rays usually found in P. scalare. While it can be difficult to count these on a moving fish, a clear photograph can help you verify this detail at home.
This increased ray count contributes to the incredible vertical height that Altums are famous for. A mature specimen can reach a total height of over 12 inches, making them much taller than they are long.
Comparing Altums and Scalare Varieties
It is very common for retailers to label “Peruvian Altums” or “Rio Nanay” angels as true Altums because they share a similar brownish hue and tall stature. However, these are distinct species with different care requirements and growth potentials.
In a thorough angelfish care guide, you will notice that standard angels are much more forgiving of water chemistry. True Altums are sensitive specialists that require very specific conditions to thrive and maintain their health.
To help you visualize the differences, I have compiled a comparison table based on the most common traits seen in the hobby.
| Feature | True Altum (P. altum) | Common Angel (P. scalare) |
|---|---|---|
| Head Shape | Pronounced Supraorbital Notch | Straight or Slightly Curved |
| Dorsal Ray Count | 27 to 30 Rays | 23 to 26 Rays |
| Body Coloration | Silvery-bronze with red spots | Highly Variable (Silver, Marble, Gold) |
| Maximum Height | Up to 15+ Inches | Up to 8-10 Inches |
| Natural Range | Rio Orinoco & Rio Atabapo | Widespread across the Amazon Basin |
Coloration and Banding Patterns
While color can be influenced by diet and mood, true Altums have a very specific “look” that is hard to replicate. They often display a base color that shifts from silver to a warm, toasted bronze or brownish-green.
One of the most beautiful traits of the Pterophyllum altum is the presence of small, rust-red spots or striations on the body and fins. These spots become more prominent as the fish matures and settles into a low-stress environment.
The vertical bars on an Altum are also very wide and dark, often appearing almost black when the fish is excited. You will notice four primary bars, with the first passing through the eye and the last at the base of the caudal fin.
The Importance of the Reddish Hue
If you observe an Altum from the Rio Atabapo, you will often see a much deeper red coloration in the fins compared to those from the main Orinoco. This is likely due to the high concentration of humic substances in their native blackwater.
When I first started keeping wild Altums, I noticed that their color would fade significantly if the water was too hard or alkaline. Maintaining a proper natural river habitat is essential for their visual identification and health.
Without the right water chemistry, the distinct bronze sheen can turn into a dull gray, making them look like a standard silver angelfish. This is why many hobbyists fail to realize they have a true Altum until the fish is properly acclimated.
Environmental Clues: Blackwater and Conductivity
Understanding how to identify a true altum angelfish also involves knowing where they come from and what they need. These fish are extreme blackwater specialists, living in water that is essentially “liquid peat.”
In their native Rio Orinoco and Rio Atabapo, the water has a low conductivity, often measuring near zero. This means the water is incredibly soft and acidic, sometimes with a pH as low as 4.5.
If a seller claims to have tank-bred Altums that thrive in hard, tap water with a high pH, be skeptical. While some breeders are successfully raising Altums in more moderate conditions, true wild-caught specimens will struggle outside of a blackwater biotope.
Common Mistake: Many beginners confuse the “Peru Altum” (Rio Nanay) with the true Altum because the Rio Nanay variety also has a tall body. However, the Rio Nanay fish lacks the deep supraorbital notch and the high dorsal ray count of the true species.
Challenges in Identifying Juvenile Altums
Identifying these fish becomes significantly harder when they are young. At a size of two or three inches, the supraorbital notch is not always fully developed, and the fins may not have reached their majestic proportions.
This is the stage where many misidentifications happen. Sellers may unintentionally (or intentionally) label wild-caught scalare as Altums to command a higher price.
When buying juveniles, I always look at the spacing between the vertical bars. In true Altums, the bars appear more “compressed” relative to the body height compared to young scalare.
Furthermore, look at the overall body shape. Even as youngsters, Altums should appear “taller” and more laterally compressed than their cousins. If the body looks round or disc-shaped like a silver dollar, it is likely not a true P. altum.
Setting Up a Home for True Altums
Once you have successfully mastered how to identify a true altum angelfish, the real work begins. These fish are not for the faint of heart or the inexperienced keeper.
Because of their extreme height, they require very tall aquariums. A standard 55-gallon tank is often too shallow; I recommend a tank that is at least 24 to 30 inches tall to allow for full fin expansion.
You will also need to focus heavily on specific water parameters to keep them healthy. This includes using Reverse Osmosis (RO) water remineralized to very low levels and adding tannins through Indian Almond leaves or driftwood.
Feeding and Growth
True Altums can be notoriously finicky eaters when first introduced to an aquarium. In the wild, they prey on small crustaceans and insect larvae, so they often ignore dry flakes or pellets initially.
I have found that starting them on live baby brine shrimp or frozen bloodworms is the best way to get them feeding. As they grow, they will become more opportunistic, but they always appreciate a protein-rich diet that mimics their natural food sources.
Watch their growth rate carefully. A true Altum that is healthy and well-fed will grow vertically at a surprising rate. If your “Altum” stops growing at 8 inches of height, it was almost certainly a misidentified scalare.
Frequently Asked Questions (FAQ)
Can true Altums live with other fish?
Yes, they can live with peaceful tank mates that share their water requirements. However, avoid small tetras like Neons, as a large Altum will eventually view them as a snack. Discus and larger tetras like Rummy Nose or Bleeding Hearts make excellent companions.
Are there tank-bred true Altums available?
Yes, thanks to dedicated breeders like Simon Forkel, tank-bred Pterophyllum altum are becoming more common. These are often easier to keep than wild-caught specimens because they are already acclimated to aquarium life and commercial foods.
Why are true Altums so expensive?
Their price reflects the difficulty of collection in remote areas of Colombia and Venezuela, as well as the high mortality rate during transport. Additionally, their slow growth and specific breeding requirements make them a premium species in the hobby.
Is the “Peru Altum” a real Altum?
Technically, no. The “Peru Altum” is a trade name for a specific locality of Pterophyllum scalare found in the Rio Nanay. While they are beautiful and tall, they do not possess the unique morphological traits of the true Orinoco Altum.
How long do true Altums live?
With proper care, a true Altum can live for 10 to 15 years. Their longevity depends heavily on maintaining pristine water quality and a low-stress environment.
Conclusion
Mastering how to identify a true altum angelfish is a rite of passage for many serious aquarists. It requires moving past the labels on the glass and looking at the biological reality of the fish in front of you.
By focusing on the supraorbital notch, the dorsal ray count, and the specific bronze-red coloration, you can avoid the common pitfalls of misidentification. These fish are the true royalty of the Amazonian rivers, and they deserve a keeper who understands their unique nature.
If you are ready to take the plunge, ensure your tank is tall enough and your water is soft enough. The reward of seeing a group of true Orinoco Altums gliding through a well-scaped tank is unlike anything else in the fish-keeping world.