Early signs of this disease are greyish-white marks or patches around the mouth, or on the body or fins of the fish. These may appear thread-like, particularly around the mouth, giving rise to the incorrect name of 'mouth fungus'. Fins will deteriorate and sores may appear on the body. The gills may be affected, giving rise to bacterial gill disease. It may cause 'shimmying' behaviour in fishes like livebearers.

The disease is caused by the bacteria Flavobacterium colmnare, formerly known as Flexibacter columnaris. It has been refered to as 'mouth fungus' (even though the cause is bacterial), due to the whitish strands which may appear fungus-like. These are Gram-negative, rod shaped bacteria, which move by gliding across a surface.

As with many bacterial diseases, poor water quality is a major factor in triggering the disease. Sudden changes in conditions may also trigger it, and the disease is common in newly imported fish.

Anti-bacterial medications should cure this disease if used promptly. At later stages, the bacteria may invade internal organs, in which case only antibiotics may be effective. Several strains exist which vary in their virulence (how 'aggressively' they cause disease)..

This disease is characterised by a swollen or hollow abdomen. Swollen areas may exhibit a 'pine-cone' appearance caused by the fishes scales sticking out. Fish may also appear off-colour and listless, and may stop feeding. The swelling caused by this disease may often be mistaken for a pregnant or egg-carrying fish. Gouramies and Cyprinids (barbs, danios, etc) are prone to this disease.

Dropsy is a condition with several possible causes. It may frequently be caused by internal infections by a number of different bacterial species. Viruses have also been associated with the disease. Poor water quality and/or diet may trigger the disease. If the problem has been caused by permanant damage to the kidney, then treating the infection will not eradicate the symptoms.

This disease must be caught early to maximise the chance of saving an affected fish, and even then the disease is difficult to cure. Previously, antibiotics prescribed by a vet were the only means of treatment for those countries (including the UK) where antibiotics cannot be purchased over-the-counter. There are now commercially available remedies which may help. These include Interpet #9 Anti Internal Bacteria and Waterlife's Octozin. The addition of salt (1 tsp/gallon) may also be beneficial.

Dropsy is not usually considered to be particularly contagious, so it should not spread to other healthy fish - dead fish should be removed immediately however, to avoid cannibalism. However, bear in mind that there is more than one cause of dropsy, so in some cases the infective agent could be contagious. It is preferable to carry out treatment in a hospital tank where available.

The fins become opaque and ragged, and may be blood-streaked. The fin erosion may continue until it reaches the base of the fin, at which point fish usually die. It is therefore important to catch this disease early.

The disease is caused by various bacterial species, which are normally present in aquarium water, but do not infect healthy fish. The disease is usually triggered by poor water quality or where fin damage has occured, often caused by fin-nipping fish.

Commercial anti-bacterial remedies are available to destroy the bacteria and halt the damage. The commercial products available include Waterlife Myxazin, Interpet #8 Anti Fungus and Finrot and Maracyn by Mardel Labs. .

Cotton-wool like growths on the body of the fish, usually greyish-white, but can be darker. Some bacterial diseases may be mistaken for fungus, including the so-called mouth fungus, which is actually caused by bacteria.

Fungal spores are always present in the aquarium, and an outbreak of fungal disease usually occurs after damage to the fishes skin or gill area, and as a secondary infection.

Commercial anti-fungal remedies can be used to destroy the fungus and prevent it spreading. These include Interpet #8 Anti Fungus and Finrot and Waterlife Protozin. Most medications avaialble for treating fungal infections will also treat bacterial infections, providing a safety net in the case of mis-diagnosis..

Rapid gill movements, and swollen or discoloured gills. The fish are likely to stop feeding and may gasp either at the surface or laying motionless on the bottom.

The disease can be caused by infections of fungi, bacteria and parasites, and poor water quality is likely to be a contributory factor.

An improvement in water quality may be the first step in treatment - avoid overfeeding and overcrowding, and carry out frequent partial water changes. Use a water conditioner during water changes to avoid irritation of the gill membranes by chlorine. It may be necessary to add an anti-bacterial to the water. If gill parasites are suspected, it may be necessary to treat with formalin or copper based medications.

The main symptom of this disease is the small pits, mainly on the head, which give the disease its name. These are usually whitish in colour, and there may be yellowish mucus trailing from them. The fish may also stop feeding and become hollow bellied.

The disease affects mainly cichlids, particularly oscars and discus, but can also affect gouramies.

The disease is linked with a protozoan parasite, Hexamita (sometimes known as Octomitus). This may often be present at low levels in fish, but the acute infection does not occur unless factors like poor water quality or poor diet have an influence. Therefore, Hexamita alone may not be the primary cause, and good water quality and a varied diet should prevent this disease occuring.

The fish can be treated by isolating to a separate tank and adding either Dimetridazole (5 mg/litre) or Metronidazole (7 mg/litre). In some countries (including the UK), these are only likely to be available via veterinary prescription. The treatment will probably need to be repeated a few days apart, with a 20-30% water change between each treatment. Medicated food is useful for treatment, but this can be problematic if the fish is not feeding. Direct injection near the affected area is likely to prove very effective, but should only be attempted by an appropriately qualified person. In the UK, Waterlife Octozin may also be used for HITH disease.

It also appears that a cure is sometimes possible simply by an improvement in water quality and diet in some cases.

The main symptom of this disease is the small sugar-grain like spots which give the disease one of its common names. Fish may also rub against hard objects. In advanced stages, fish may be observed gasping and gill damage may be apparent.

The disease is caused by a protozoan parasite, Ichthyophthirius multifiliis, and is very contagious. The parasites spend a portion of their life cycle embedded beneath the skin of the fish, where they feed from the body tissue. The white cyst in which they are enclosed gives the characteristic white spots. Adults emerge from these cysts and fall to the floor of the aquarium, where they multiply inside a protective capsule. Some time later, the capsule bursts, releasing hundreds of free-swimming infectious parasites which attach themselves to new hosts. Whitespot is often introduced with new fish which have not been quarantined. Outbreaks of whitespot often occur after fish have been exposed to cooler than normal temperatures. Clown loaches are particularly prone to whitespot.

There are two main approaches to curing whitespot, and opinions vary on which is the more effective. There are several effective commercially available remedies, normally based on malachite green and formalin. Note that malachite green is hard on scaleless fish like catfish and loaches, and also other fish such as tetras. Some alternative medications are based on copper and formalin. The other method employed is to add salt to the tank (gradually), up to a level of 6-8 tsp per gallon. Note that fish vary in their tolerance of salt, and for more sensitive soft-water species, it may be better to use 3-4 tsp per gallon maximum. Higher salt levels may also affect plant growth.

In either case, increasing the temperature should kill the parasite off more quickly, because it will speed up the life cycle of the parasite, so that the free-swimming stage is reached as quickly as possible - this is the only stage affected by medications. However, increasing the temperature means there will be less oxygen dissolved in the water (some medications can lower it too), so ensure the tank is well aerated, and do not raise the temperature beyond around 28^oC (82^oF).

Due to the life cycle of the parasite, the whole tank must be treated, in order to kill the parasites which are not attached to fish. Therefore it is not appropriate to treat only the affected fish in a separate isolation tank.

Effective commercial remedies include Protozin by Waterlife and Maracide by Mardel Labs. In more recent times, resistant strains of the whitespot parasite seemed to have emerged, some of which are difficult to treat - it may be necessary to try a different treatment if the medication is not effective within 6-7 days.

This disease was originally described in Neon Tetras, but can affect many other species of fish. In Neons, one of the early signs of this disease is a loss of the red colour, and difficulty swimming Note that there is a so-called "false neon disease", which is bacterial, and shows very similar symptoms. It is impossible for the home aquarist to determine for certain the difference between NTD and false NTD on the basis of visible symptoms alone, without laboratory backup. This disease has also been confused with Columnaris.

The disease is caused by a microsporidian parasite. The disease is most likely to be passed on from newly acquired fish, which have not been quarantined.

These parasites are very resistant to medications, and there are no proven effective treatments. Some anti-parasite medications claim to treat this disease, but their effectiveness is debatable. Some apparant 'cures' may have been the result of successful treatment of false-NTD. The best course of action is to isolate sick fish quickly, and maintain good water quality to reduce the chances of more fish succumbing to the disease. The use of a diatom filter, which can reduce the number of free parasites in the water, may help. .

The visible symptom of this disease is a fine grey-gold to whitish 'dust' on the body of the fish. Fish will usually show very rapid gill movement.

The disease is caused by a protozoan parasite, and may be triggered by exposure to ammonia and nitrite, or excessive nitrate levels.

There are effective commercially available remedies, including Waterlife Protozin (UK and elsewhere), and Maracide by Mardel Labs (US and elsewhere). Begin treatment as soon as possible.