Aquatics - Fish Health


Causes of Disease in Fish

  • water quality issues
  • feeding issues
  • pathogens
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  • single-celled organisms
  • Found everywhere!
  • Some are helpful, and some are pathogens
  • can only effect if the fish is immunocompromised
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  • single celled organisms
  • can have ciliates
  • 10-52 micrometres
  • many are symbionts, some are parasites
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  • group containing yeast and moulds
  • unicellular or multicellular
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  • 25,000 species, half are parasitic
  • Found in nearly every ecosystem in the world
  • Examples are roundworms
  • tail is tapered
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  • parasitic flatworms (flukes)
  • usually have two suckers to stick to the fish and to feed with
  • endoparasite
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  • class of parasitic worms most of which have a gut with an intestine and a pharynx
  • series of hooks to attach to the fish with, can cause irritation
  • adults are hermaphrodites
  • mostly found in fish, one found in mammals
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Also known as Ich or white spot disease. Caused by the protozoa Ichthyophthirius multifiliis. When the fish is healthy it is unlikely to be infected with Ichthyophthirius, it is when the fish is stressed that the immune system is compromised and the fish can therefore be infected. Some common stresses that can result in Ich include:

  • improper water and/or temperature condition of the aquarium
  • fighting other inhabitants of the aquarium
  • an improper or unhealthy diet
  • handling/shipping of fish
  • introducing an infected fish or decoration

It is more often detected in freshwater aquariums, although it has been known to affect saltwater aquariums as well. Some fish keepers believe that smaller fish and fish that are less likely to get stressed are less likely to be infected by Ich

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Ichthyophthirius: Symptoms

Early symptoms of Ichthyophthirius include scratching against rough surfaces, looking disorientated when swimming and keeping their fins folded against their body.

White spot disease becomes more evident when the fish develop small raised white spots, that may look like sand grains, covering the body, gills and fins. They often start off visible on just the fins and spread as time goes on. The fish may also experience a loss of appetite, swim to the surface as it tries to breathe and have a cloudy appearance to its eyes.

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Ichthyophthirius: Treatment

In order to treat an Ich infection, it is important to treat the entire tank and not just the infected fish. This is because by the time you spot the Ich infection on one fish, it is likely the whole tank has been infected. The protozoa is only vulnerable to treatment during the time they are multiplying into smaller infectious units, if these smaller units do not find a host within this time then they die. 

The lifecycle of the protozoa is dependent on the tank temperature. If the tank temperature is raised to 25°C to 29°C so the time that treatment is needed reduces as the lifecycle is shorter. 

Most treatments for Ich contain the active ingredient formalin or malachite green, either individually or in combination. There are other combinations that include methylene bluecopperquinine hydrochloridepotassium permanganate and sodium chloride baths that are also available. However, the formalin/malachite green treatment is often recommended as it is believed to the most effective and more easily available. It is suggested you consult a fish vet before beginning any treatment to find out whether any of the ingredient in the treatment can be harmful to your fish. 

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Ichthyophthirius: Prevention

In order to prevent Ich it is suggested that:

  • you only purchase fish that are healthy and are free from all signs of disease
  • never buy a fish from a tank that contains a dead or diseased fish
  • always place new fish in a proper quarantine tank for a minimum of two weeks
  • never buy plants from a source that keeps them in a fish tank with fish. If you do, quarantine the plants for at least 4 days
  • purchase fish from as direct a source as possible to reduce transport stress
  • avoid fluctuations in temperature, pH, or ammonia levels
  • always feed a variety of properly stored food
  • do not overstock the tank
  • maintain excellent water quality by doing regular water changes
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Camallanus is a nematode worm that is most strongly associated with fish species such as guppies, mollies, loaches, dwarf cichlid fish, angelfish and discus. However, most types of aquarium fish can be affected. The main cause for Camallanus worms is lack of maintenance and cleaning of the fish's environment. 

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Camallanus: Symptoms

Light infections of Camallanus are hard to detect. Serious infections can be spotted by the presence of red, thread-like worms emerging from the anus of the fish, the mature worms are a couple of millimetres long. Other symptoms can include bloating, wasting and a disinterest in food. Well-maintained fish can be infected without showing any symptoms. It is possible for the worm to damage the host fish if other factors are at play, including:

  • overcrowding 
  • poor diet
  • poor water quality
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Camallanus: Treatment

Antihelminthic medications are the most important type of treatment for Camallanus worm infections. Options for medication include fenbendazole, levamisole, and praziquantel. These treatments do not necessarily kill the worms, in most cases just paralysing them. Within 24 hours of treatment the aquarium substrate should be thoroughly cleaned to remove the worms. Normally three treatments are required that are a wekk apart.

It must be noted than Antihelminthic medications are usually toxic to snails and shrimp, so these animals should be removed before the use of the medication. When treating expensive or delicate fish it is advised to seek veterinary advice before starting treatment as in excessive doses the treatment can be toxic to fish. 

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Camallanus: Prevention

Camallanus worms can be prevented by quaratining new stock and treating prophylactically with antihelminthic medications. Fish food that contains crustaceans should also be avoided unless it can be guarenteed they come from a pond with no fish. 

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A common disease in goldfish, Costia is caused by a parasiteCostia can be a fast killer as the parasite attaches to the fish's gills. 

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Costia: Symptoms

  • slimy patches around the head and gills
  • small haemorrhages under the chin
  • sudden death
  • awkward swimming
  • gasping at the surface of the water
  • appetite loss
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Costia: Treatment

Raising the water temperature and/or salt dips can prove effective against the disease. Also changing 40% of the aquarium water can be effective when treating Costia. When treating with salt it is best to start with three or four grams of salt per litre of water. It can also be treated with Formalin, which is the best option if the strain has become resistant to salt. 

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Costia: Prevention

Quarantining and treating any new fish or plants is key to prevention an infestation.

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A saucer-shaped parasite that attacks the skin and gills of fish. An infestation is caused by either poor water quality or overcrowding.

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Trichodina: Symptoms

The disease causes severe stress as your fish will rub itself against surfaces and damage its skin and gills. This scratching can lead to bacterial and ulcer infections. Symptoms in goldfish include:

  • scratching and flashing
  • ulcers
  • stop feeding
  • fish may isolate themselves
  • lay at the bottom with clamped fins
  • lethargic
  • irritated skin
  • greyish, white film over the fish's body
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Trichodina: Treatment

You can use salt treatments or medicated treatments like potassium permanganate or Malachite Green with Formalin or using Proform C (for colder tanks) and QuickCure (for warmer tanks).

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Trichodina: Prevention

Prevent infection by quarantining any new fish. You also need to keep water high quality and prevent overcrowding. 

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Bacteria is the pathogenic cause of mycobacteria

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Mycobacterium: Symptoms

There are not many symptoms known for fish, but marine mammals can show skin lesions when they have the bacteria. The disease is also zoonotic so humans can also suffer symptoms. However, in fish the disease is usually characterised by wasting.

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Mycobacterium: Treatment

There is no vaccine or satisfactory treatment for Mycobacterium.

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Mycobacterium: Prevention

You can prevent mycobacterium by quarantining and pursuing biosecurity

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