Info about Incorporating
Coping with Parasitic Problems in Your Aquarium
While some of the major and most common parasitic illnesses are the result of infection by a single type of protozoan, others can be caused by a range of different organisms. Some of these microscopic parasites represent a major health hazard in the aquarium, and are difficult to eradicate.
• Hole-in-the-head
This condition is associated with cichlids, especially discus (Symphysodon aequifasciata). It is the result of infection by a protozoan parasite called Hexamita, which is sometimes present in the digestive tract of this group of fish, where it normally causes no harm. If the fish are weakened by stress, however, the parasite multiplies and the fish's condition deteriorates.
One of the earliest signs of this disease are small pale areas visible on the head. Left untreated, these pale areas coalesce, causing erosion of the tissue, which also opens the way for secondary infection. Medicating the water with specific drugs of the metridazole group can overcome the infection before it develops into a life-threatening condition. Even if the fish recovers, scarring is likely, so rapid treatment is vital to minimize damage. Another sign is the presence of abnormal whitish faeces, which tend to hang behind the fish as it swims, indicating a disturbance to the digestive tract.
Outbreaks are commonly linked with stress, but adding vitamin C to the fish's diet (which is now routinely included in most formulated foods) should help to prevent outbreaks of hole-in-the-head, as will incorporating greenstuff in the form of some kind of vegetable matter. Research indicates that there may also be a link betwen water quality and this disease. Discus have highly specific needs in terms of water conditions, and, if these are not met, they may be more prone to attack from Hexamita parasites.
• Slimy skin
This infection may involve a variety of different pathogens, and results from an increased output of mucus by the fish's body, in response to skin irritation. The fish's skin takes on a greyish-white colour, which tends to obscure the coloration beneath. A number of different protozoa can cause this problem, and secondary bacterial infections often also occur. It may usually be treated successfully, if caught at an early stage.
• Other non-specific infections
A wide range of microbes including protozoa may also be implicated in cases of gill disease. This is relatively common in newly-acquired fish, which show obvious signs of discomfort when breathing, with rapid gill movements suggesting that they are having difficulty in drawing enough oxygen from the water. They will also be less active than normal, sometimes remaining inert for long periods.
Careful management is required to ensure the fish's recovery. Although poor environmental conditions almost certainly contributed to their condition in the first place, it is not a good idea to transfer the fish to dechlorinated fresh tap water, especially if a water conditioner is accidentally omitted. It is better to place them in an isolation tank containing equal amounts of aquarium water and treated tap water. Maintain the temperature at a slightly higher level than normal, because this helps to improve their immune response.
• Pop-eye
In cases of exopthalmia, the eyes protrude abnormally, giving rise to its alternative name of pop-eye. The condition may result from quite a wide range of causes. It may be linked with eye flukes or a bacterial infection such as piscine tuberculosis, and either one or both eyes may be affected. If there is just an isolated case, then the cause is more likely to be parasitic rather than bacterial. Poor water quality is sometimes implicated in severe outbreaks of pop-eye. In order to treat the condition effectively, it is important to know the cause.
• Internal parasites
It is often very difficult to recognize the signs of internal parasites (the helminths group), because the symptoms are less obvious and distinctive than in conditions caused by external parasites. For example, if a fish is suffering with a severe intestinal build-up of parasitic worms, it may appear slightly swollen and show difficulty in swimming, but these symptoms are not enough to make a diagnosis, and they could be linked with other conditions such as dropsy.
Fortunately, internal parasites are generally unlikely to become established in an aquarium, simply because they have complex life cycles which involve both other vertebrates and invertebrates. The fish is merely the intermediate host, meaning that the parasite does not mature in its body. This later stage in its life cycle normally occurs only in the wild when the infected fish is eaten by a bird such as a kingfisher or by a mammal.
The immature larval tapeworms develop in the intestinal tract of the bird, and start producing eggs which are released from the body in the bird's droppings. The eggs are consumed by crustaceans, so fish can become infected by eating these invertebrates. Within the regulated and restricted habitat of the aquarium, daphnia given as live food can represent a threat to the fish, acting as possible intermediate hosts for the parasites at this stage. Only daphnia cultured in an environment where birds could not foul the water can be regarded as safe.
If these helminths do gain access to the fish's body, they may then escape from the intestines into the body cavity and continue their development there. In other cases, the helminths remain within the fish's intestinal tract. They may occasionally be noticeable, looking like a fine strand of white ribbon trailing from the fish's anus. Symptoms of infection in this case are far less common, aside from a general loss of condition.
In some cases, treatment may be successful, although it will help greatly if the parasite can be correctly identified in the first instance. There are many potential types of parasitic worms that may occasionally afflict fish, but it is typically individuals caught from wild habitats that are at greatest risk, rather than the majority that are reared on fish farms.
• Eye flukes
Flukes in general may be recognized by their flattened shape. As with parasitic worms, their life cycles tend to be complex - with the notable exception of the skin fluke (Gyrodactylus) - so they are not a common problem in aquarium surroundings, nor is there a great risk of cross-infection.
The basic route of infection is similar to that of internal parasites, but the eggs hatch into free-living larvae, which seek out and infect aquatic snails. After beginning their development, the larvae then leave the mollusc and attack fish, boring into their bodies.
In the case of eye flukes, they migrate to this area of the body, and in mild cases, they -will cause cloudiness and opacity of the affected eye. A large accumulation of these parasites may result in the lens becoming ruptured, resulting in blindness. Treatment is virtually impossible in any event, but fortunately, these parasites are rare in aquarium fish.