This ciliate infect the fins and gills of fish causing signs such as respiratory distress (increased opercular rate, piping for air at at the surface), clamped fins, depression, and excess mucus production.  Its marine counterpart is Brookynella. These ciliates are easily identified microscopically by their heart-shape and slow circular motion^5,6.  They are usually easy to treat with formalin, malachite green or salt (see medication section).

The picture below illustrates Chilodonella under the microscope.