Learning about protozoan parasites isn’t exactly the first thing most people think of when pondering the thought of a new aquarium. But having a basic knowledge of these pesky little critters is a good idea in the event your aquarium fish become victims. In this article you’ll get practical tips on preventing and treating protozoan parasites in your aquarium.
Learning about protozoan parasites isn’t exactly the first thing most people think of when pondering the thought of a new aquarium. But having a basic knowledge of these pesky little critters is a good idea in the event your aquarium fish become victims. In this article you’ll get practical tips on preventing and treating protozoan parasites in your aquarium.
There seem to be countless diseases that can afflict your aquarium fish and they all have different causes, symptoms and treatments. The average aquarium hobbyist may easily be overwhelmed by the sheer volume of ways their fish might become sick. When it comes to aquarium fish diseases, you don’t need to know everything – but having a basic knowledge about the different types of diseases is a good start. One of the larger categories of fish diseases includes a variety of protozoan parasites. In order to protect your fish from these parasites you should learn what they are, where they come from, and what you should do if they enter your tank.
What is a Protozoan?
Protozoa are single-celled, eukaryotic organisms that can only be seen through a microscope. These organisms are found most often in bodies of water and in soil. Most protozoa are harmless but there are some disease-carrying types which can infect your tank and your fish, causing them to become ill. There are four types of protozoa – flagellates, ciliates, amoebas and sporozoa. Protozoa are divided into these categories based on their means of locomotion, or the way they move.
Flagellates move through the use of flagella, whip-like organelles which often appear in pairs. Ciliates are covered in hair-like organelles called cilia which function much like flagella but are shorter and often appear in larger numbers. Amoebas are shapeless single-celled organisms that move with the help of pseudopods, or false feet. These organisms stretch one part of themselves out and the rest of it moves to follow. Sporozoans are exclusively parasitic and they possess an apicoplast, an organelle designed to help penetrate host cells. While all sporozoans are parasitic, not all flagellates, ciliates and amoebas are – it simply depends on the genus of the particular protozoa.
What Are Protozoan Parasites?
A protozoan parasite is simply a type of protozoan that has acquired the ability to invade the bodies of host organisms and to live in their cells and tissues. Protozoan parasites cannot live outside the host body. In the aquarium, this means that protozoan parasites cannot survive in tank water – they live inside the bodies of fish and are transferred through waste or the consumption of an infected fish. Infections caused by protozoan parasites typically manifest in the form of spots or patches of damaged or discolored skin on the bodies of host fish. Parasites can also cause internal damage which may not be obvious until the fish loses its appetite or the ability to swim properly.
Common Protozoan Parasite Diseases in Fish
Ichthyophthirius multifilis – More commonly known as Ich, this parasitic infection is one of the most common diseases affecting aquarium fish. Ich is caused by the ciliate protozoan Ichtyopthirius which has a direct life cycle – this simply means that once the parasite enters the host body, it lives most of its life there, even reproducing from within the host body. These parasites may reach approximately 1mm in size and appear on the skin and gills of fish like small white spots. Fish that are infected with this parasite may flash, or turn over in the water, or they may pipe, or float near the surface of the water breathing through their mouths.
Trichodinia – Another type of ciliate protozoan, these parasites are saucer-like in shape and are ringed entirely with cilia. These parasites typically inhabit the gills of fish where they may cause breathing difficulty – fish with cutaneous infections may also pipe and flash. In chronic cases, fin erosion and ulcerations have been observed. These parasites have a simple, direct life cycle and reproduce through cell-splitting. They can be transmitted to other fish through either direct contact or infected water.
Hexamita – These parasites are flagellates, possessing three pairs of anterior flagella that measure approximately one and a half times the length of the body. Hexamita parasites typically cause damage within the intestinal tract of infected fishes which may lead to symptoms similar to those caused by malnutrition. These organisms are not well understood and are believed to be one possible cause of lateral line erosion in fish, a condition more commonly known as hole-in-the-head disease.
Ichthyobodo – More commonly known as Costia, these parasites are flagellate organisms that have a direct life cycle. In their free-swimming form, these parasites have two pairs of flagella and the attached form typically adheres to the gills and skin of host fish. Costia infections present symptoms like increased mucus production, ulceration, fin erosion and hyperplasia of the skin and gills.
Chilodonella – A ciliate protozoan, Chilodonella is a motile organism which affects the skin and gills of host fish. This parasite is typically heart-like in shape and is entirely covered in cilia. This disease can be difficult to diagnose but treatment is typically successful if a diagnosis is made before any permanent damage has been done to the host fish. Infections caused by Chilodonella may cause symptoms such as rapid breathing, excessive mucus secretion, appetite loss, clamped fins and lethargy.
Plistophora hyphessobryconis – Commonly known as Neon Tetra Disease, this disease is caused by the sporozoan Plistophora hyphessobryconis. Though first observed in neon tetras, this disease can affect a variety of other fishes including Danios, Goldfish, Minnows and Angelfish. This parasite typically enters the host body through accidental ingestion and, once inside it spreads throughout the body of the host fish and reproduces in the form of spores. These spores may be released into the aquarium through the expulsion of waste or they may be transferred to new hosts if the host fish is consumed by other fish.
Tips for Preventing and Treating Protozoan Diseases
Because the most common way protozoa are introduced into the tank is through infected fish, it is wise to quarantine all new fish for at least two weeks before adding them to the tank. It is not always possible to tell by looking at a fish if it is suffering from or carrying a disease, so instituting a quarantine policy is the only way to be safe. Maintaining high water quality in your tank is also very important in preventing all kinds of fish diseases, not just protozoan infections. When the water quality in your tank drops the water chemistry may change and your fish could become stressed. Stressed fish are much more susceptible to disease, so while poor water quality may not directly cause infections it may increase the likelihood that they will occur.
When it comes to treating protozoan diseases, one of the most effective things you can do is to interrupt the life cycle of the parasite. In many cases, increasing the tank temperature will speed up the life cycle of the parasite, causing it to die faster. Many aquarium hobbyists swear by salt baths as a means of treating many aquarium fish diseases. If your fish are suffering from an external protozoan infection, this method may help to kill off the parasite. If you are able to identify the disease affecting your fish you may also be able to find a medication designed to treat it. Treatments like methylene blue and malachite green may be effective against protozoan infections like Ich. When treating your fish for disease, always remember to remove the activated carbon from your filter because it will remove the chemicals which make the treatment effective.
