The health risk from parasites is far less than the risk from “unseen” illness causing bacteria which are present in almost all foods.
Roundworms called nematodes are the most common parasite found in marine fishes. Some people call these nematodes herring worms or cod worms. Actually, several different species exist and it is hard to distinguish between them. All are in the family Anisakidae and are anisakid nematodes (see information below).
Common Freshwater Fish Parasites Pictorial Guide: Sessile Ciliates
It's called , described by the Centers for Disease Control and Prevention as a parasitic disease caused by worms that attach to the wall of the esophagus, stomach, or intestine. The best ways prevent it is to avoid eating raw or undercooked fish or squid.
Common Freshwater Fish Parasites Pictorial Guide: Motile Ciliates
The branchiurans, often called lice, have flattened bodies adapted for rapid movement over the skin surface. By means of hooks and suckers, they periodically attach for feeding by inserting the piercing mouth part (stylet) into the skin. Sea lice () are a significant disease problem of pen-reared salmonids. Consultation with a salmonid health specialist is suggested if these parasites are encountered, because treatment options are limited and environmental concerns are significant. spp are commonly found on aquarium, pond-reared, and wild freshwater fish.
Common Freshwater Fish Parasites Pictorial Guide: Flagellates
Just like any other creature, your fish can suffer from disease and parasites. When fish have parasites they are very contagious. If a fish actually has parasites, it's highly recommended to separate the fish in question from all the other aquatic life in your fish tank. Taking the fish out of the aquarium into a portable container is probably the best way to do so. Otherwise the parasites will most likely spread through the whole fish tank until all fish are infected. Below is a list of seven parasites that are common among tropical fish: Anchor worms – these parasites are females and have an anchor shaped head, which they use to burrow its way into the flesh of its prey. Once they bury themselves into the fish there may be a little bit of bleeding on the fish where the head has attached itself. You may also be able to see a little worm or tentacle that is white protruding out from the spot where the parasite is attached. Because this parasite’s head is anchor shaped it is difficult to remove, and if pulled out by force may cause the fish to suffer a bleeding wound. Fish lice -- this parasite is tricky because it is so hard to spot. This parasite will hide itself by taking on the same color as its host. The host fish will try to get rid of the lice by rubbing its body against stones, plants or along the side of the tank in an effort to try and remove them. Ichthyophthirius – The so-called 'ich' or 'white spot' is the most common tropical fish disease, caused by probably the most common freshwater parasite. The typical behavior of an infected fish includes loss of appetite, rubbing itself against objects, flashing and hiding abnormally. Once a fish in your fish tank is infected, quarantine is necessary to prevent the fish from spreading the tropical fish disease to the other tank inhabitants.