Costiasis

Signs of infection include excess mucous production, respiratory distress, lethargy, clamped fins, general debilitation and resting on the substrate.

The parasites feed on the gill and skin cells and can quickly kill fish by depriving them of oxygen and allowing secondary infection of fungus and bacteria in to the wounds.

Epistylis

Infection starts when the skin or fins of the fish have already been injured. They form colonies that grow all over the fins and skin and form a cotton-like structures that look much like fungal infection. Red sore and opercular perforation can be observed.

Ichthyophthiriasis (ICH)

The disease is caused by the ciliate protozoan Ichthyophthirius multifiliis, commonly called ich or ick. Fish infected with ich typically develop small, blister-like, raised lesions (white spots) on the skin and/or fins. If the infection is restricted to the gills, however, no white spots will be seen.

Myxosporidians infestation

Myxobolus cerebralis is a myxosporeanparasite of salmonids (salmon, trout, and their allies) that causes whirling disease in farmed salmon and trout. Whirling disease afflicts juvenile fish (fingerlings and fry) and causes skeletal deformation and neurological damage. Fish "whirl" forward in an awkward, corkscrew-like pattern instead of swimming normally, find feeding difficult, and are more vulnerable to predators. The mortality rate is high.

Trichodiniasis

Clinical signs of Trichodiniasis in fish are sluggish movement, loss of appetite, black colouration, necrosis and ulcer on different parts of the body, detached scales and excessive accumulation of mucous in gill pouches.