Angelfish are susceptible to the same diseases as other freshwater aquarium fish. And prevention and treatment for these diseases are similar to any other fish species. For the best treatment outcome, you will need to positively identify the disease affecting your angelfish. When in doubt, take your fish and a water sample to your local fish store for help.
The only angelfish specific virus is called the Angelfish Virus. It was prevalent among breeders during the 1980s and has been called the angelfish plague and angelfish AIDS. It was caused by fish with the disease introduced from Southeast Asia and the first large outbreak has infamously become known as the angelfish plague of 1986. Symptoms of angelfish virus include lethargy, the fish tends to point his nose up and not move, swimming unnaturally with fins kept close to the body (clamped fins), and excessive slime that may drip off the body of the fish.
In the original angelfish plague, aquarists reported fins eroding down to the body in a matter of hours and bleeding gills. Cases of angelfish virus today do not usually have such severe symptoms. Since that first outbreak, the virus seems to have weakened, or the angelfish population is more resistant to the more severe forms of the disease, or a new but similar virus has emerged. Whatever the case, it’s still a deadly disease. It’s believed that the virus weakens the fish and allows secondary infections to quickly set in. Most angelfish do not survive and die within a couple of days. It’s highly contagious and will spread to all other angels in the tank. Water from one tank infected with this disease has the potential to infect another tank.
As with any fish viral disease, there is not a treatment for angelfish virus other than supportive care by keeping the tank clean and warm. Some recommend antibiotics to control secondary infections. However, many aquarists will cull angelfish showing symptoms of this freshwater angelfish disease so as not to spread the virus. If any angelfish survive the disease, they will be carriers and still able to pass the virus to other angelfish for up to six months.
Bacterial Infections in Fish
Bacteria are present in all water and not all bacteria are bad. They may become a problem to the fish if the tank is overcrowded, needs a water change, or if the fish have reduced resistance. Bacterial infections are hard to identify and hard to treat. The bacterium has to be identified for best treatment, and antibiotics for fish tanks also kill the good bacteria. Signs of bacterial infections include fin rot, mouth rot, skin ulcers, pale coloring, and emaciation. If you suspect a bacterial infection, remove the sick fish and treat it in a separate isolation tank.
Fungal Infections in Fish
Open sores and wounds have the possibility of attracting fungus. Poor water quality gives the fungus the opportunity to attack a fish. A white cottony growth on a fish is the mark of a fungal infection. Do an immediate 20 to 30 percent water change. The best recommendation is to use a general fungal treatment available from the local fish store. If only one fish is affected, isolate that fish in a quarantine tank for treatment.
Hole-in-the-Head and Lateral Line Disease in Fish
Cichlids, including angelfish, are particularly susceptible to hole-in-the-head disease. In the beginning of this disease, small wounds or enlargements of the pores on the head and along the lateral line appear. These wounds eventually open up to produce large holes in the head of the fish.
The cause of hole-in-the-head disease is still under speculation. Fish expert Joseph Levine writes in The Complete Fishkeeper that “many aquarists believe that it is brought on by a long-term nutritional deficiency and then aggravated by invading protozoans.” He goes on to state, “among tangs, surgeonfish, and angelfish…the syndrome is often associated with a lack of fresh plant material in the diet.” The Bailey Brothers of AquariumFish.net believe that under-gravel filters and sometimes canister filters may contribute.
Whatever the cause, the consensus is that changes to improve the care of your angelfish or other fish will prevent hole-in-the-head disease. Regular water changes, a nutritional diet that includes plant matter, and proper filtration should mostly prevent hole-in-the-head disease for angelfish. Vitamin C rich foods, such as spinach, can sometimes cure mild forms of this disease. Increasing the temperature to 90 degrees can also help. Increase the temperature slowly by a degree or two every two hours. Most angelfish can tolerate such high temperatures, but tank mates may not so move your angelfish to a hospital tank before trying this treatment. To treat severe cases of the disease, the most recommended medical treatment to add is a metronidazole fish medication. Metro+ Hole-in-head/Leteral Line Treatment by Aquarium Solutions can be added to the water or to your angelfish’s food for systemic treatment.
With most diseases in fish, a partial water change is the first place to start treatment. Most are also preventable with regular water changes and providing good care to your angelfish. If the condition is treatable, several commercial products are easily available. Read and follow the instructions carefully for any medication used.