About Fish Parasites

As you watch your fish, you notice that a couple of them are hovering near the bottom of the tank, listless and uninterested in the food you have just fed them. As you look closer, you notice that the fish are covered in tiny white dots. If you have ever experienced something like this, you have experienced parasites in your fish tank. Fish parasites are common, but they can be deadly to your fish. Learning about them before you have an outbreak in your tank will help you to keep your fish healthy.

  1. Function

    • A parasite is a living organism that lives on or in a host's body. The parasite uses something from the host to live. Some parasites and hosts live together harmoniously, but in a fish tank, most parasites are harmful to their hosts. The nutrients that they take from the host in order to live are nutrients the host needs for survival. When your fish are overcome by a parasitic infection, they become listless and sick, and they may die.

    Significance

    • Fish parasites often show up on fish when water quality drops. This does not mean that they are not present in the water when it is clear, as most tanks have some parasitic organisms in them. However, parasites tend to attack fish when they are weak, injured or stressed. Healthy fish in a low-stress environment can typically ward off any parasites they come in contact with. When water quality drops, however, fish are more susceptible to parasites due to stress, and this is when signs of a parasitic infection are noticed.

    Symptoms

    • Fish that have a parasite are typically lethargic. They may have torn or damaged fins. Swimming near the bottom of the tank is a common symptom, and fish infected with ich or gill flukes will usually rub against rocks or substrate. Sometimes a parasitic infection will cause the fish to develop ugly gray patches on the skin. Other infections cause large, open sores on the body. Fish with parasites may exhibit involuntary spasms and typically have little appetite.

    Types

    • Ich is one of the most common parasites and causes small white dots on the fish's body. Gill flukes are another common parasite, which is characterized by gill irritation and difficulty breathing. Anchor worm is a parasite that attaches to the fish's body and looks like a white-red worm about ¼ of an inch in length. If a fish becomes covered in black spots, it is another parasite known as black spot. Costia is a parasite that causes a gray-white, mucous-like film all over the body. Hole-in-the-head is a disease caused by the parasite hexamita, which causes large sores typically on the head.

    Prevention/Solution

    • The best prevention for parasites is proper water maintenance. Avoid overcrowding your fish tank, and do not add sick or damaged fish to your aquarium community. Remember that parasites are probably already in your water, so work hard to keep it clean and healthy to ensure your fish are not stressed. If you do notice a parasitic outbreak, treat the entire tank with an over-the-counter parasite remedy. Even though some fish are not sick, if one has succumbed they have all been exposed.