Aquarium tropical fish and fish diseases




Latin name: Ichthyobodo necatrix, Costia necatrix
Other names:
Pathogen: parasite

Symptoms: Flagellates 8-15 micrometers large of different form which depends on the relative position to the observer. There are two flagella on the front part of the organism, Clamped fins, Fish do swinging movements, Fish itch (fish scratch on the rocks and other objects), Fish stop feeding, Laboured breathing, Blue-grayish slime coating, Entire body covered whith gray coating, Fins stick together, Fraying of fins, Separate slightly red areas on the body, Separation of fin rays, Slime comes out of gills

Scratching against hard objects, awkward swimming with fins clamped and the appearance of a velvety grayish or bluish film on the fish's body, caused by excessive slime production, is a characteristic of the disease. If the gills are badly affected, fish show signs of asphyxia, even though the oxygen level in the aquarium is normal. Gills are anemic and are covered in mucous which blocks the absorption of the dissolved oxygen. Fish will stop feeding. Sometimes fin disintegration will occur, which is characterized by the necrosis of tissues between fin rays. Denudation of fin rays is observed.

Costia is an invasive disease that affects many aquarium and free-living fish. It is caused by
the flagellate Ichthyobodo necatrix, formerly known as Costia necatrix, a member of the Family
Bodonidae, Order Protomonadina. It is very small, 8-15 micrometers in diameter. At the anterior end, the protozoan has two flagella by means of which it swims and attaches itself to the skin and gills burrowing itself into the outermost epidermal cells and feeding on their content. Microscopically, the flagellate will have different shapes (oval, cone-shaped, or curved). It is not uncommon to see four flagella two small and two big ones. This is explained by the parasites ability to multiply rapidly. The second pair of flagella will indicate that the flagellate has started dividing. In its center, the parasite has an oval nucleus. There are different vacuoles and inclusions in the protoplasm. Costia necatrix will infect the skin and gills. The parasite can only survive for a few hours without a host. Costia necatrix has a very simple life cycle. Once on the host, Costia infects the outermost epidermal cells of the skin and gills. It grows rapidly and begins to multiply by longitudinal division. It is yet unclear whether unfavorable conditions can cause the flagellate to get back to the cyst stage (encystment). It is only known that if conditions deteriorate, Costia becomes round in shape. The parasite multiplies most rapidly at temperatures of 25 to 28C (77-82F). However, it does not tolerate temperatures above 3032C (86-89F). Outbreaks are most common in nursery tanks due to overcrowding. Adult fish rarely die of Costia, but their become carriers of disease. Clinically, chilodotiasis, trichodinosis and gyrodactylis often resemble Costia. That is why the diagnosis should be based on clinical signs of disease as well as microscopic examination of scrapings of the skin and gills.

Microscopic examination is carried out with a microscope at medium power with a half-closed diaphragm. Only experts can carry out microscopic examination with a microscope at low power.

How to cure:
Sick fish are to be treated in a separate tank. Treat fish with a series of short-term baths: potassium permanganate solution (KMnO4), for five days
sodium chloride solution (NaCI), for seven days. Artificial seawater can be used.
pure copper sulfate solution (CuSO2*5H2O), daily for four days.
Malachite green solution
Basic violet K solution
Formaline solution
Bicillin-5 solution

If it is impossible to treat fish in a separate tank the following medications are added into the main tank: Trypaflavine, Malachite green with copper sulfate, Rivanol, methylene blue, Bicillin-5.

Water, gravel, and plants need not be taken away from the main tank after fish have been moved to the hospital tank. Without a host, parasites die within 24 hours. As a preventive measure, water temperatures can be raised to 3234C (90-93F) for two days. Once the treatment is over, fish are reintroduced into the aquarium and are given large amounts of fresh feed.

SERA Costapur
Sera Ectopur

TetraMedica ContraIck
TetraMedica General Tonic

Aquarium Pharmaceuticals General Cure
Aquarium Pharmaceuticals All-Natural Melafix

Potassium permanganate solution sodium chloride
Pure copper sulfate solution
Malachite green solution
Basic violet K solution
Formaline solution
Bicillin-5 solution

Newly bought fish are quarantined for 30 days. Before introducing new fish into the aquarium, give them three short-tem therapeutic baths. Do not let water from the tank get into live feed. It is not advisable to introduce pond plants without first disinfecting them. Nets, scrapers, feed boxes, thermometers, pulverizers and other equipment should not be shared between several aquaria.

Fish susceptible to the disease/disorder:
All aquarium fish are susceptible to disease, primarily young fish. Outbreaks occur all year round, but most often at the beginning of summer.