Fish lice (fish argulus sp.)

Signs of infection are discoid parasites with diameters ranging from 8 to 12 millimeters and come in a variety of colors, from light green to brown. You can see them affixed to the fish body and fins.

Infested fish lice can damage many kinds of cold-water fish. It is almost impossible to find them in tropical species unless parasites are brought into the aquarium on live bait or plants. Even then, fish lice can't survive in warm water for a long time.

This parasitic crustacean has eight feathery legs, and they swim on their legs in search of host fish. The small tail is used to control direction and contains reproductive and respiratory organs. On the ventral side of the worm, two powerful suckers make the fish lice stick firmly to the scales of the host. Between the two suckers is a poison needle, which can inject an anticoagulant into the fish and connect it to the body tissue.

There are about 200 species of fish lice worldwide. The most common are foliage, white salmon and Japanese mackerel.

Fish lice usually lay eggs in midsummer and lay on stones or other solid surfaces. About a month later, the larvae hatch and swim freely until they find the host fish. When full, the larvae migrate casually from one fish to another, sometimes without eating for several days. Five or six weeks after hatching, they can reproduce. It is suspected that fish lice may spread diseases such as edema.

The recommended treatment can be used to get rid of fish lice. If necessary, gently rub the paint brush with concentrated salt water, or soak it in a salt solution to help get rid of them. The alternative is to add a new aquarium anti-crustacean treatment agent to the water. Trichlorfon is effective, but it should be used in accordance with regulations.