Freshwater angelfish (Pterophyllum) is a small genus of freshwater fish from the family Cichlidae known to most aquarists as "Angelfish". All Pterophyllum species originate from the Amazon River basin in tropical South America. The three species of Pterophyllum are unusually shaped for cichlids being greatly laterally compressed, with round bodies and elongated triangular-shaped dorsal and anal fins. This body shape allows them to hide among roots and plants, often on a vertical surface. Naturally occurring angelfish are frequently striped longitudinally, colouration which provides additional camouflage. Angelfish are ambush predators and prey on small fish and macroinvertebrates. All Pterophyllum species form monogamous pairs. Eggs are generally laid on a submerged log or a flattened leaf. As is the case for other cichlids, brood care is highly developed.
Pterophyllum altum, (common name: Altum Angelfish or Orinoco Angelfish) occurs strictly in the Orinoco River Basin and the Upper Rio Negro watershed in Southern Venezuela, Southeastern Colombia and extreme Northern Brazil.[1] Its natural color is also silver but with three brownish/red vertical stripes and red striping patterns into the fins. The species may show red spotting when mature and when aroused exhibits a black operculum spot. Characteristic of this species is an acute incision or notch above the nares. All true (pure) 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", will most likely not show this trait or show it to a much lesser degree. The true wildcaught Orinoco Altum is among the most challenging among tropical fish to breed in captivity. The species is the largest of the genus and specimens exceeding 50 cm in height (from tip of dorsal to tip of anal fin) have been reported in the wild; in aquariums, specimens are known to have grown to +40 cm. 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 Guainía floodplain where the Rio Negro is born, before entering Brazilian territory. Unlike P. scalare which prefer to spawn on plants, P. altum prefers to spawn on submerged roots and tree branches. This species is recommended for intermediate to advanced aquarists due to the detailed maintenance it requires for proper health.
Angelfish are kept in a warm aquarium, ideally around 80°F (27°C). They will do best if fed a mixture of flake, frozen and live food. Care should be taken to not overfeed, they will continue to eat even what they do not need. This will lead to a bulidup of fats resulting in inactivity and early death. Angelfish will do best if kept in an acidic environment, pH should be below 7.5 (note: 7.5 is still slightly alkaline - acidic is defined as below 7.0). Although most aquarium-bred angelfish can survive in a wide range of pHs, wild-caught angelfish will need water with a pH of at most 6.5. Even though angelfish are a member of the cichlid family they are generally peaceful, however; the general rule "big fish eat little fish" applies. Other aggressive fish should not be kept with angelfish because their flowing fins are vulnerable to fin nipping! Some smaller more aggressive fish may even nip at the fins of these fish. Sometimes the rule "Big fish eat little fish" Isn't true, many people have successfully kept fullgrown Angels with small Tetras and other varieties of small fish.
P. scalare is relatively easy to breed in the aquarium, although one of the results of generations of inbreeding is that many breeds have almost completely lost their rearing instincts resulting in the tendency of the parents to eat their young. In addition, it is very difficult to accurately identify the gender of any individual until they are nearly ready to breed.
Angelfish pairs form long-term relationships where each individual will protect the other from threats and potential suitors. Upon the death or removal of one of the mated pair, some breeders have experienced a total refusal of the other mate to pair up with any other angelfish; others have had more success with subsequent mates. Both parents care for the young.
Depending upon aquarium conditions, P. scalare reaches sexual maturity at the age of six to twelve months or more. In situations where the eggs are removed from the aquarium immediately after spawning, the pair is capable of spawning every seven to ten days. Around the age of approximately three years, spawning frequency will decrease and eventually cease.
When the pair is ready to spawn, they will choose an appropriate medium upon which to lay the eggs and spend one to two days picking off detritus and algae from the surface. This medium may be a broad-leaf plant in the aquarium, a flat surface such as a piece of slate placed vertically in the aquarium, a length of pipe, or even the glass sides of the aquarium. The female will deposit a line of eggs on the spawning substrate, followed by the male who will fertilize the eggs. This process will repeat itself until there are a total of 100 to up to 1200+ eggs, depending on the size and health of the female fish. The pair will take turns maintaining a high rate of water circulation around the eggs by swimming very close to the eggs and fanning the eggs with their pectoral fins. In a few days, the eggs hatch and the fry remain attached to the spawning substrate. During this period, the fry will not eat and will survive by consuming the remains of their yolk sacs. At one week, the fry will detach and become free-swimming. Successful parents will keep close watch on the eggs until they become free-swimming. At the free-swimming stage, the fry can be fed newly-hatched frozen och fresh brine shrimp. Freshwater angelfish is notably difficult to breed in an aquarium environment.
