Pterophyllum altum, also known as Altum Angelfish or Orinoco Angelfish
Can only be found in the Orinoco River and Upper Rio Negro in Southern Venezuela, Southeastern Colombia and extreme Northern Brazil.
The largest angelfish among its kind, exceeding 50 cm in height. (from tip of dorsal to tip of anal fin)
The color is silver but with three brownish/red vertical stripes and red striations into the fins. The species may show red spotting and a blueish green dorsal overcast when mature and when aroused exhibits a black operculum spot. Characteristic of this species is an acute incision or notch above the nares (supraorbital indention).
All true Orinoco Altum specimens show this trait, whereas commercial hybrids product of crosses to Pterophyllum scalare, that are occasionally performed by breeders to sell them as "Orinoco Altum", may not exhibit the trait or it may appear in a lesser degree.
The true wildcaught Orinoco Altum is among the most challenging among tropical fish to breed in captivity. Most Altum Angels are more frequently found in the well oxygenated, extremely soft waters of Upper and Middle Orinoco tributaries shed from the Guyana Shield Highlands, preferring a pH range between 4.5 to 5.8. These are very transparent blackwaters with almost nil conductivity. Temperature range in these waters is between 78°F (26°C) and 84°F (29°C). They are also found in the Atabapo River and Inirida River floodplain, down the Casiquiare and GuainĂa floodplain where the Rio Negro is born, before entering Brazilian territory. Unlike P. scalare(mentioned above) which prefer to spawn on the submerged leaves of plants and trees in the flooded rainforest, P. altum prefers to spawn on submerged roots and tree branches in a moderate water current. This species is recommended for intermediate to advanced aquarists due to the detailed maintenance it requires for proper health.