There isn't enough that can be said about the diseases that affect
tropical fish. And as far as I have heard, there is only one full time
veterinarian of fish in the United States. Which leaves us pretty much on
our own to become our own little doctors of our aquatic friends.
I will discuss here only a small portion of some of the more common ailments. Do not take what is written here as carved in stone. I have been fortunate enough not to have suffered any of the following problems in my tanks, yet. So needless to say I personally have no experience in treating diseases myself. This information here is the results of my research in the area. I feel that I should be a little prepared and knowledgeable in the area, so I will be able to hopefully prevent, recognize, and handle any maladies that may come my way. The use of a quarantine/hospital tank is always recommended for new and sick fish.
A seriously ill fish, with an incurable disease should be disposed of humanely. Do not flush live fish down the toilet. Throwing a fish hard against a solid floor will kill the fish instantly and end it's suffering.
White Spot: Ichthyophthiriasis or "ich" for
short, is the most widespread and dangerous disease that can affect both
coldwater and tropical fish and is highly contagious. It is caused by a protozoan
which embeds itself in the skin of the fish and causes a small white blister
to form. In a few days this blister will enlarge and then burst. The adult
parasite falls to the bottom of the tank, and then forms a cyst that will
produce up to 2,000 free-swimming young and start the cycle again. At
temperatures between 69.8F and 78.8F (21-26C) the cycle completes in about
8 to 10 days. At lower temperatures the cycle could take a few weeks to complete.
The first symptoms to be observed is the fish begins to "scratch" itself against plants, rocks and other objects. Visible white spots, up to 1mm in diameter, will then begin to form. The actual earliest stages will affect the gills, causing heavy breathing and the itching, however the visible spots will usually first be seen on the fins.
The Guppy (Poecilia reticulata), Head and Tail Light Tetra (Hemigrammus ocellifer), and the Ruby Barb (Puntius nigrofasciatus) are some of the fishes that are more susceptible then others.
Ich is highly contagious, so all care should be taken not to transfer it to other tanks. It is possible to transport it via nets, hands, plants, etc., but it can only be transferred by a wet object(s). So if a tank is emptied and let to stand dry for a couple of days, the tank itself will become sterile of the parasite. It needs to find a new host within a matter of a few days or die. However many aquarists find it extremely difficult to eradicate the disease completely without thorough disinfection of all plants, fishes, and the tank.
It is easier to attack the disease parasites in the free-swimming stage, rather than after the host has been affected. The white spots that are already existing on a fish are resistant to some forms of treatment. There are several chemicals that can be used in the treatment, and to enhance these, raise the water temperature to 86F. (30C.). At this high temperature however, the water will not hold much dissolved oxygen so added aeration is required to keep it oxygenated sufficiently.
TREATMENT: Malachite green is the main ingredient in most commercial cures for ich. It comes in different strengths, depending on the manufacturer, and most can be used repeatedly until the disease is conquered as long as the directions and limits are followed closely. The treatment should last for a period of no less than ten days to be certain that all free-swimming and offspring parasites will be treated. Some smaller fishes, such as the small tetras, are sensitive to malachite green so only half the recommended dosage should be used.
Quinine is another effective treatment as long as the dosage recommended by the manufacturer is followed. It can be administered as a hydrochloride or as a sulphate.
Dropsy: True dropsy is usually caused by Aeromonas punctata,
which is a bacterial infection that attacks the kidneys and other organs
to cause an upset in the water balance. It can be recognized by a swelling
of the fish that may become severe enough to cause the scales to protrude
and the fish resembling a porcupine. There is another form that appears to
be dropsy, but which actually is not, that has the same symptoms minus the
TREATMENT: Phenoxethol may be given in a dosage of 10-20 ml of a 1% stock solution per liter gradually added over a 24 hour period. In severe cases it can be surgically treated by an expert , by puncturing the fish and withdrawing the fluid.
Tuberculosis: Tuberculosis is due to a variety of organisms and causes
emaciation. Some of these organisms are thought to be related to the human
form, however there is no chance of infection. A symptom of tuberculosis
in tetras is two light yellow spots on the caudal peduncle.
Fin and Tail Rot: Ragged, filmy fins and tail and possibly even bloody
streaks in the fin are symptoms of this bacterial disease. Adult fish and
fry that are overcrowded are susceptible.
TREATMENT: Improve the environment and increase the aeration. In addition add up to 1% of chloromycetin in the food for seven days. Feed small amounts of dried or prepared food, so it will be gobbled, mixed with the powder from the capsule. Enough chloromycetin will be consumed to treat the fish from the inside out.
If you experience feeding problems, try the use of acriflavine, or maybe a combination of the two. Acriflavine should not be used for a period of more than 10 days, as it has been known to create reproductive problems. By adding one teaspoon of uniodized salt and raising the temperature to 80.6F (27C) will increase the effectiveness. Raising the temperature however, decreases the oxygen content in the water making extra aeration an added requirement. Acriflavine comes in different forms ranging from a crystalline, diluted liquid, to a mixture with other chemicals. It is important to follow the correct dosage given by the manufacturer.
Velvet: Odinium limneticum is the protozoan which causes this
dangerous disease. The symptoms resemble those of white spot, in that the
host becomes affected with a few yellow dots in the beginning and eventually
becoming covered with them. The fish will seem to have been dusted with a
gold or yellow powder. To distinguish the difference between the two, is
in the coloration of the spots. Velvet is golden or yellow in color, while
white spot is, of course, white.
Odinium will attach itself to the body of the fish and penetrate the skin growing deeply using pseudopods. When the parasite reaches maturity, it will drop off the host falling to the bottom of the tank. There it becomes enclosed in a cyst and begins to divide internally. After a couple of days, as many as two hundred new free-swimming dinoflagellates emerge and the cycle repeats multiplied. The parasites are found in many tanks, but don't become problem unless the fish have become weak from chilling or other difficulties.
Velvet is fatal to young fish and must be treated immediately, while the adult may have it and show no signs of distress. But if the adult is to be used for breeding, it's offspring will acquire the disease. The most susceptible types of fish are Cyprinids, Labyrinth fish, and the Egg-laying toothcarps.
TREATMENT: Acriflavine should not be used for a period of more than 10 days, as it has been known to create reproductive problems. By adding one teaspoon of uniodized salt and raising the temperature to 80.6F (27C) will increase the effectiveness. Raising the temperature however, decreases the oxygen content in the water making extra aeration an added requirement. Acriflavine comes in different forms ranging from a crystalline, diluted liquid, to a mixture with other chemicals. It is important to follow the correct dosage given by the manufacturer.
Copper salts can also be used. Copper sulphate is toxic to velvet, but it is to the fish as well. A middle point has to be found where the disease is killed and the fish are not. Turn off all carbon filters and add five drops per 4 liters (1.24 gallons) of a 1% solution of copper sulphate repeated every three days. If you can find it, copper citrate may be used at half this dosage. When you turn back on the carbon filter, it will rapidly remove the copper leaving only a harmless trace amount.
DO NOT introduce new fish to the treated water. During treatment, if the fishes stop feeding, gasp at the waters surface, or show any other signs of discomfort, turn on the carbon filter to remove the copper.
A combined cure of acriflavine and copper may be necessary because it is difficult to combat this resistant disease. After all signs of the disease have faded, keep watch for a reoccurance.
Neon Tetra Disease: Neons affected will show the symptoms of a fading
of the blue-green line with the eventual loss of the color almost completely.
Their swimming will become erratic, and there will be a loss in weight. The
disease is not restricted to neon tetras and can affect other small fishes
such as Glowlight tetras and Zebra danios.
Exotic Tropical Fishes; T.F.H. Publications 1996
The Aquarium Fish Survival Manual; Barron's 1985
Important note: You should not rely on the veterinary advice or information provided on this site for diagnosis or treatment of any specific situation. Always consult your own veterinarian for specific advice concerning the medical condition or treatment of your own animal.