Protozoan Fish Diseases

Velvet or Rust
Symptoms: Clamped fins, respiratory distress (breathing hard), yellow to light brown "dust" on body.

This disease has the appearance of a golden or brownish dust over the fins and body. The fish may show signs of irritation, like glancing off aquarium decor, shortage of breath (fish-wise), and clamping of the fins. The gills are usually the first thing affected. Velvet affects different species in different ways. Danios seem to be the most susceptible, but often show no discomfort. This disease is highly contagious and fatal.

The best treatment is with copper at 0.2 mg per liter (0.2 ppm) to be repeated once in a few days if necessary. Acriflavine (trypaflavine) may be used instead at 0.2% solution (1 ml per liter). As acriflavine can possibly sterilize fish and copper can lead to poisoning, the water should be gradually changed after a cure has been effected.

Costia
Symptoms: Milky cloudiness on skin.

This is a rare protozoan disease that causes a cloudiness of the skin. The best treatment is with copper at 0.2 mg per liter (0.2 ppm) to be repeated once in a few days if necessary. Acriflavine (trypaflavine) may be used instead at 0.2% solution (1 ml per liter). As acriflavine can possibly sterilize fish and copper can lead to poisoning, the water should be gradually changed after a cure has been effected.

Raising the water temperature to 80? - 83? F for a few days has also been effective.

Hexamita
Symptoms: The first symptom of slimy, white mucous feces, even while still eating and acting normal. Further signs are the fish hiding in the corner it's head down, head above the eyes gets thin, they blacken in color, and swim backwards.

Hexamita are intestinal flagellated protozoa that attack the lower intestine. Discus and other large cichlids, especially Oscars, are especially prone to Hexamita. As it is a disease of the digestive tract, a wasting away or loss of appetite may be experienced.An effective treatment is the drug metronidazole. A combined treatment in the food (1% in any food the fish will eat) and in the water (12 mg per liter) is recommended. Repeat the water treatment every other day for three treatments.

(This disease is often confused with another disease called Head and Lateral Line Erosion (HLLE), which use to be called "hole-in-the-head" disease, because both these diseases are often seen simultaneously in the same fish. Head and Lateral Line Erosion disease looks like cavities or pits on the head and face. It is not a protozoan disease, but is actually caused by environmental conditions.)

Ich (Ichthyphthirious)
Symptoms: Salt-like specks on the body/fins. Excessive slime. Problems breathing (ich invades the gills), clamped fins, loss of appetite.

Ich, Ick, white spot disease, whatever the name, this is the most common malady experienced in the home aquarium. Luckily, this disease is also easily cured if caught in time! Ich is actually a protozoa called Ichthyophthirius multifiliis. There are three phases to the life cycle of this protozoa. Normally, to the amateur aquarist, the life cycle is of no importance. However, since Ich is susceptible to treatment at only one stage of the life cycle, an awareness of the life cycle is important.

Adult phase - it is embedded in the skin or gills of the fish, causing irritation (with the fish showing signs of irritation) and the appearance of small white nodules. As the parasite grows it feeds on red blood cells and skin cells. After a few days it bores itself out of the fish and falls to the bottom of the aquarium.
Cyst phase - after falling to the bottom, the adult parasite forms into a cyst with rapid cell divisions occurring.
Free swimming phase - after the cyst phase, about 1000 free swimming young swim upwards looking for a host. If a host is not found within 2 to 3 days, the parasite dies. Once a host is found the whole cycle begins anew.

These three phases take about 4 weeks at 70? F but only 5 days at 80? F. For this reason it is recommended that the aquarium water be raised to about 80? for the duration of the treatment. If the fish can stand it, raise the temperature even higher up to 85?.

The free swimming phase is the best time to treat with chemicals. Raising the aquarium temperature to 80? F will greatly shorten the time for the free swimming phase to occur. The drug of choice is quinine hydrochloride at 30 mg per liter (1 in 30,000). Quinine sulphate can be used if the hydrochloride is not available. The water may cloud but this will disappear. By reducing the time (with raised temperature) of the phases, you should be able to attack the free swimming phase effectively.

Some aquarists like to use malachite green, but it tends to stain the plastic and silicone in the aquarium. Most commercial remedies contain malachite green and/or copper, which are both effective.

Neon Tetra Disease
Symptoms: Whitened areas deep into the fishes' flesh. Muscle degeneration leading to abnormal swimming movements.

So named for the fish it was first recognized on. It is caused by the sporozoa Plistophora hyphessobryconis. Even though it is named after Neon Tetras, it can appear on other fish. Whitish patches appear as if just below the skin. In Neon Tetras it destroys the bright blue-green neon stripe. The organisms form cysts which burst and release spores. The spores penetrate further and form more cysts. Eventually, the spores migrate to the water and are eaten by other fish in the food. These spores migrate into the digestive tract, then the muscles, and a new infection starts.   

There is no known cure. It is best to destroy the infected fish and clean the aquarium.

Glugea and Henneguya
Symptoms: Similar to Lymphocystis, the fish will have nodular white swellings on fins or body.

Glugea and Henneguya are sporozoans that form large cysts on the fish's body and release spores. Luckily, these diseases are very rare. The fish bloat up, with tumor like protrusions, and eventually die.  

No cure, as of yet. It is best to destroy the infected fish before the spores can spread.

Chilodonella
Symptoms: Dulling of the colors due to excessive slime, fraying of the fins, weakness, gill damage

This disease causes a blue white cloudiness on the skin and attacks the gills. Later the skin may be broken down and the gills destroyed. The fish may behave like they have irritations, by glancing off aquarium decor, they may have clamped fins and difficulty breathing.

Acriflavine (trypaflavine) may be used at 1% solution (5 ml per liter). As acriflavine can sterilize fish, the water should be gradually changed after a cure has been effected. It also helps to raise the temperature to about 80? F.