The freshwater Angelfish, Pterophyllum scalare, is without question one of the most popular fish in the trade. Domestication has contributed enormously to both its popularity and to the ease with which it is now bred both commercially and by intermediate and advanced hobbyists. In addition, geneticists have worked out the heritability of many of the color, finnage, and pattern variation now available. Angelfish enthusiasts should be on cloud nine.

Unfortunately, commercial production of Angels has taken a turn for the worst. But before we discuss that, let's go over some of the common problems that can plague the home hobbyist . . . .
Originating from South America, Angelfish evolved out of waters with lower pH, lower total dissolved solids, lower hardness and lower alkalinity. In the wild, therefore, unionized ammonia and nitrite levels were essentially zero. This helps explain why Angels need excellent water quality, and any hobbyist who has worked with them can attest to this fact. Domestic Angels are an enigma. In some respects, they are much tougher than their wild counterparts, of course. Many more people can keep them and many producers and hobbyists successfully breed Angels in hard water with more alkaline pH! But at the same time, these domestics, in particular the man-made variants, are much more delicate . . . .

Poor water quality, rough handling and improper nutrition will all lead to problems including opportunistic infections. Angelfish are susceptible to many of the opportunists which attack other ornamentals, although some are more common than others. Some of the bacterial opportunists include Aeromonas hydrophila, Aeromonas salmonicida and Pseudomonas sp., all of which can cause bacterial septicemia and/or ulcerations. Columnaris disease, caused by Flexibacter columnaris, is also fairly common, especially on long-finned or veiled varieties exposed to poor water quality. Columnaris commonly manifests itself as whitish areas along the edges of the fins, which can progress to a raggedy appearance and even to stumps. Columnaris can also attack the body.

Click on pictures to enlarge. All photos: MFJacobs
A magnificant wild Angel with a
highly inbreed German Red Angel.

In addition to bacterial infections, many different parasites can pay a visit to stressed and weakened Angels. Chilodonela, a ciliated protozoan, can overcome Angels swiftly and cause major mortality, without any obvious signs besides behavior. Usually the Angels will appear weak and lethargic and lose buoyancy control, often drifting in the current of the tank. Angels are susceptible to other parasites as well, including Ichthyophthirius, Ichthyobodo and Tetrahymena, but again, there is usually an environmental component to the disease which triggers the outbreak.

Monogenetic trematodes, or flukes, are also fairly common, especially on the gills.
Certain internal parasites are almost a given in Angelfish, many most likely normal fauna and expected in low numbers. However, stressed and immunocompromised fish can become weakened further by massive parasitic outbreaks. In particular, Spironucleus (formally called Hexamita) can erupt into incredibly high numbers (thousands to tens of thousands) in the intestines of sick Angels and lead to their further demise. Angels with Spironucleus infections often exhibit weakness, lethargy, abdominal or coelomic distention, and loss of buoyancy control (sometimes floating on their side at the top of the tank). In addition, these fish often shed stringy "mucousy" feces. Spironucleus infections in broodstock have been linked to decreased reproductive efficiency and fry survival. Roundworms, especially Capillaria, are also fairly common in Angels and, when present in high enough numbers, can lead to problems.
Viruses have been blamed for numerous Angelfish deaths, both commercially and in the hobby, although none of these claims have been proven conclusively, partly because of the difficulty of working with viruses. Numerous types of viruses have been visualized using electron microscopy in tissues of sick or dead Angels and include, among others, paramyxovirus, iridovirus, herpesvirus, and retrovirus. Lip tumors on Angels may have a viral component to them. But is a virus the cause for the industry wide "Angelfish Problem"?

Click on pictures to enlarge. All photos: MFJacobs
Another highly inbred strain of
Angel . . . the popular Koi Angel.

Angelfish, many of you know, have gone through several rough periods commercially and are in the midst of one now. First there was the Far East Angelfish crisis, which decimated production over there and to my knowledge, has never been completely understood. Soon after, large scale commercial Angelfish production in the US underwent similar problems. Several years ago, University of Florida faculty, Ruth Francis-Floyd, Craig Watson and others, working with producers, looked into this crisis extensively, but were unable to pinpoint a single factor, virus or otherwise.

As seen in other large scale, intensive aquaculture production systems, disease and the environment will frequently find new ways to kill intensively produced fish. The channel catfish industry is a good example of this. In the wild, catfish experience no where near the stresses they do in captivity and production systems as well as inbreeding can concentrate previously widely dispersed pathogens and susceptibilities. ESC, enteric septicemia of catfish (also known as "hole-in-the-head" disease), caused by Edwardsiella ictaluri, and CCV, channel cat virus, were previously not seen until production intensified and brought all the right factors into play. Now these are among the leading causes of mortality in the catfish industry.

Many different factors, including the nebulous "stress of intensive production," which encompasses a wide and varied scope of problems, have contributed to the commercial Angel problem. Although viruses have not been positively proven to be causal in some mass mortalities, they still cannot be completely ruled out. Much of the problem may merely be one of diagnostic technology not being fine tuned enough. However, viruses are seldom the only cause. Could massive inbreeding be a contributor? There is good reason to believe that the founder population of all Angels currently bred in captivity was very small. The products of this very biased gene pool may be experiencing problems similar to those of the incredibly inbred wild cheetah. More genetic work may give us clues to this potential cause. What about other pathogens which may be harder to find? Although an easy and often used "cop-out," this possibility still cannot be ruled out. The question becomes one of approach to the problem and diagnostic tools. Although outwardly breeding practices are rather standard, upon closer inspection the many numerous "tricks" employed by breeders to maximize production make industry wide epidemiological studies a bit more difficult. Until we can solve the commercial problem, the hobby will continue to rely more heavily on other smaller scale or advanced hobbyist sources. Take care of your Angels and your reward will be great . . . .