|This article needs additional citations for verification. (May 2013)|
G. Cuvier, 1831
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, Orinoco River and Essequibo River basins in tropical South America. The three species of Pterophyllum are unusually shaped for cichlids being greatly laterally compressed, with round bodies and elongated triangular 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.
There are currently three recognized species in this genus:
- Pterophyllum altum Pellegrin, 1903
- Pterophyllum leopoldi (J. P. Gosse, 1963)
- Pterophyllum scalare (Schultze, 1823) (Freshwater angelfish)
The freshwater angelfish (Pterophyllum scalare) was described in 1824 by F. Schultze. Pterophyllum is derived from the Greek pteron (fin/sail) and phyllon (leaf).
In 1906 J. Pellegrin described P. altum. In 1963 P. leopoldi was described by J. P. Gosse. There may still be undiscovered species in the Amazon River. New species of fish are discovered with increasing frequency, and, like P. scalare and P. leopoldi, the differences may be subtle. Scientific notations describe the P. leopoldi as having 29–35 scales in a lateral row and straight predorsal contour. Whereas, the P. scalare is described as having 35–45 scales in a lateral row and a notched predorsal contour. The leopoldi show the same coloration as P. scalare. P. leopoldi can show a faint stripe between the eye stripe and the first complete body stripe and a third incomplete body stripe between the two main (complete) body stripes that extends three-fourths the length of the body. Whereas, P. scalare's body does not show the stripe between the eye stipe and first complete body stripe at all, and the third stripe between the two main body stripes rarely extends downward more than a half inch, if even present. P. leopoldi fry develop three to eight body stripes, with all but one to five fading away as they mature, whereas P. scalare only have two in true wild form throughout life.
Angelfish were bred in captivity for at least 30 years prior to P. leopoldi being described.
Angelfish in the fishkeeping hobby
Angelfish are one of the most commonly kept freshwater aquarium fish, as well as the most commonly kept cichlid. They are prized for their unique shape, color and behavior. It was not until the late 1920s to early 1930s that the angelfish was bred in captivity in the United States.
The most commonly kept species in the aquarium is Pterophyllum scalare. Most of the individuals in the aquarium trade are captive-bred. Sometimes, Pterophyllum altum is available. Captive bred P. altum is available but occasionally. Pterophyllum leopoldi is the hardest to find in the trade.
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. While young individuals will do fine on flake, larger individuals (once they have reached dollar coin size) should be fed small pellets, as pellets are a more concentrated form of nutrition. Care should be taken to not overfeed, they will continue to eat even what they do not need to. This will lead to a buildup 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). All angelfish will prefer water with a pH of at most 7.0. Though most Pterophyllum scalare will thrive in a wide range of pH values. Even though angelfish are a member of the Cichlid family they are generally peaceful, however; the general rule "big fish eat little fish" applies. Small fish such as the Cardinal Tetra will be eaten, as they can be picked off during the night. 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. Angelfish also enjoy blackwater aquariums with plentiful wood and dark places to relax.
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, breeders have experienced both the total refusal of the remaining mate to pair up with any other angelfish and successful breeding with subsequent mates.
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 more than 1,200 eggs, depending on the size and health of the female fish. As both parents care for the offspring throughout development, 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 brine shrimp (Artemia spp.) or microworms. It is generally accepted that brine shrimp are the superior choice for fast growth rates of fry.
P. altum is notably difficult to breed in an aquarium environment.
Compatibility with other fish
In pet stores the freshwater angelfish is typically placed in the semi-aggressive category. Some tetras and barbs are compatible with angelfish, however ones that are small enough to fit in the mouth of the angelfish may be eaten. Generous portions of food should become habit, so that the angelfish don't get hungry and turn on their tank mates. Fishes that are most likely to become fin nippers (such as some barbs) should be avoided.
Aquarium Varieties of Angelfish
Most strains of angelfish available in the fishkeeping hobby are the result of many decades of selective breeding. For the most part, the original crosses of wild angelfish were not recorded and confusion between the various species of Pterophyllum, especially P. scalare and P. leopoldi, is common. This makes the origins of "Domestic angelfish" unclear. Domestic strains are most likely a collection of genes resulting from more than one species of wild angelfish combined with the selection of mutations in domesticated lines over the last 60 or more years. The result of this is a domestic angelfish that is a true hybrid with little more than a superficial resemblance to wild Pterophyllum species. It would be inaccurate to say that they accurately represent any species of wild angelfish, although they most resemble P. scalare and are frequently referred to as such.
Domestic angelfish have been bred and crossbred for several decades. There are hundreds of mutations of little importance by themselves. Much of the research into the known genetics of P. scalare is the result of the research of Dr. Joanne Norton, who published a series of 18 articles in Freshwater and Marine Aquarium (FAMA) Magazine. Those articles are reprinted at http://theangelfishsociety.org/genetics.htm .
- The silver angelfish most commonly resembles the wild form of angelfish, and is also referred to as "wild-type". It is not, however, caught in the wild and is considered domestic. The fish has a silver body with red eyes and three vertical black stripes that can fade or darken depending on the mood of the fish.
- The genetic trait for the gold angelfish is recessive, and causes a light golden body with a darker yellow or orange color on the crown of the fish. It does not have the vertical black stripes or the red eye seen in the wild angelfish.
Zebra (Z/+ or Z/Z)
- The zebra phenotype results in 4 to 6 vertical stripes on the fish that in other ways resembles a silver angelfish. It is a dominant mutation that exists at the same locus as the stripeless gene.
Black Lace (D/+) / Zebra Lace (D/+ - Z/+)
- A Silver or Zebra with one copy of the Dark gene. This results in very attractive lacing in the fins. Considered by some to the most attractive of all angelfish varieties.
- A variety with a dark brownish grey back half and dark dorsal and anal fins.
- Homozygous for Smokey with more of the dark pattern. Sometimes only the head is silver.
- Silver with a black rear portion. Halfblack can express along with some other color genes, but not all. The pattern may not develop or express if the fish are in stressful conditions.
Sunset Blushing (g/g S/S)
- The Sunset Blushing has two doses of gold and two doses of Stripeless. The upper half of the fish exhibits orange on the best specimens. The body is mostly white in color, fins are clear. The amount of orange showing on the fish can vary. On some the body is a pinkish or tangerine color. The term blushing comes from the clear gill plates found on juveniles. You can see the pinkish gill underneath.
Koi (Gm/Gm S/S) or (Gm/g S/S)
- The Koi has a double or single dose of Gold Marble with a double dose of Stripeless. They express a variable amount of orange that varies with stress levels. The black marbling varies from 5%-40% coverage.
Leopard (Sm/Sm Z/Z) or (Sm/Sm Z/+)
- The leopard is a very popular fish when young, having spots over most of their body. Most of these spots grow closer together as an adult so it looks like a chocolate with dots on it. (Smokey x Zebra)
Blue Blushing (S/S)
- This is a wild-type angelfish that has two Stripeless genes. The body is actually grey with a bluish tint under the right light spectrum. An iridescent pigment develops as they age. This iridescence usually appears blue under most lighting.
Silver Gold Marble (Gm/+)
- A Silver angel with a single Gold Marble gene. This is a co-dominant expression of Silver and Gold Marble, so you see traits of both.
- A fish that is heterozygous for Stripeless. This results in a mostly silver fish with just a stripe through the eye and tail. Sometimes portions of the body stripes will express.
Gold Marble (Gm/g or Gm/Gm)
- Depending on whether the Gold Marble is single or double dose, the marbling will range from 5% to 40% coverage.
Marble (M/+ or M/M or M/g or M/Gm)
- Marble expresses with much more black pattern than Gold Marble does. The marbling varies from 50% to 95%.
Black Hybrid (D/g or D/Gm)
- Cross a black with a gold, and you get black hybrids. A very vigorous black, that may look brassy when young. Does not breed true.
- Pearlscale is a scale mutation. The "pearlscale" angelfish is also called the "diamond" angelfish in some regions due to the gem-like iridiscence on its scales. The scale have a wrinkled, wavy look that reflect light to create a sparkling effect. Pearl develops slowly, starting at around 9 weeks of age. In can be inhibited by stressful conditions. It is recessive, requiring both parents to contain the allele. It looks best on light colored fish like Gold, Gold Marble, Albino, Silver and Zebra. It is difficult to see on dark fish and blushing angelfish.
Black Ghost (D/+ - S/+)
- Same description as a Ghost, with a darker appearance due to the Dark gene. Very similar to a Black Lace without complete stripes. Ghosts generally have more iridescence than non-ghosts.
- Albino removes dark pigments in most varieties. Some, like Albino Marble will still have a little black remaining on a percentage of the fish. The eye pupils are pink as in all albino animals. The surrounding iris can be red or yellow depending on the variety of Albino.