UK gardening help and assistance


Fish Health

(Information courtesy of Interpet Ltd)

Three Golden Rules for Healthy Fish

  1. Provide good aquarium conditions
  2. Exercise constant vigilance
  3. Accurately diagnose and treat disease

What Causes Fish Disease?

There exist many lower life forms such as virus, bacteria, fungus, protozoan and other parasites, some of which can only survive by living in or on fish. Not all of these are undesirable, although some have the potential to cause disease to their fish host and are called pathogens.

Where Does Fish Disease Come From?

  • Every aquarium naturally contains pathogenic bacteria and fungus spores as part of its normal flora and fauna.
  • Every fish also carries its own population of parasites and bacteria, some even carrying internal fungus.

With all these disease organisms naturally present it may seem surprising that fish are not constantly suffering from disease.

How Do Fish Remain Healthy?

Healthy fish like other animals have their own very effective system for fighting naturally present disease organisms called their immune system. This system creates barriers which initially prevent the disease organisms from attacking the fish. Should any disease organisms manage to breach this barrier, the immune system also has agents which actively attack the disease.

So, in a healthy aquarium the fishes' natural immune system efficiently keeps the pathogens at bay. However, there is a delicate balance that must be maintained between the fish and the disease organisms for the fish to remain healthy and disease free.

What Happens if the Balance is Upset?

If the balance between the fish and the disease organisms present in the aquarium is upset, a disease outbreak will occur. There are three ways in which this balance can be tipped:

  • By the fish becoming stressed. This reduces the effectiveness of the immune system.
  • By the population of pathogens rapidly increasing as a result of condusive conditions.
  • New disease organisms being introduced into the aquarium.

How Can Fish Disease be Prevented?

The likelihood of a disease outbreak occurring can be reduced by following these simple rules:

  • Feed a good, varied, balanced diet. A staple flake diet supplemented with frozen or freeze dried food for variety.
  • Maintain stable water quality which matches the needs of your fish. Water quality should be monitored regularly with simple to use and accurate test kits.
  • Carry out regular water changes to maintain water quality. Remember to use a water conditioner to make tap water suitable for aquarium use.
  • Use appropriate aquarium decoration, allowing sufficient hiding places and providing for any special needs of individual fish species.
  • Ensure all aquarium inhabitants are compatible. If in doubt, take the advice from your local aquatic retailer.
  • Add aquarium salt (1 gm per litre) to reduce stress in freshwater fish.
  • Maintain water clarity using aquarium treatments (such as Interpet's Filter Aid and Green Away) in combination with a good filtration system.

These steps should form a basic programme for the care of your aquarium. However, particular situations can still tip the balance and cause disease outbreaks.

Fish Stress Stress is the main cause of fish disease. Stress is caused by a number of factors, e.g. poor water quality, bullying by other fish, capture or movement of the fish, insufficient hiding places, poor nutrition. When fish are stressed their immune system breaks down allowing disease to attack.

Introducing New Fish

Fish that have become established in an aquarium develop a natural immunity to the particular disease organisms already present in that aquarium. Any new fish introduced into the aquarium may therefore be coming into contact with disease organisms for which they have not yet built an immunity. As already mentioned, fish carry their own individual population of parasites and bacteria with them. Therefore, the introduction of a new fish may result in the existing fish also coming into contact with disease organisms for which they have no immunity. Disease organisms can also be introduced into an aquarium on plants, invertebrates, live food, aquarium decorations and even nets which have been used in more than one aquarium.

Quarantine

Before introducing new fish into an established aquarium, it is a good idea to quarantine them in a separate aquarium for a minimum of two weeks, Ensure the water in the quarantine aquarium is of the same pH and hardness as that of the eventual aquarium and contains aquarium salt (2 gm per litre) to reduce stress during this settling down period. The quarantine process allows gradual recovery from the stress of being moved and time for any latent disease to develop. During quarantine take the opportunity to carry out a preventative course of treatment with a Broad Spectrum Treatment (such as Interpet's Liquisil General Tonic No. 5) to clear the fish of most common disease organisms.

Regular Preventative Treatment

A general broad spectrum treatment (such as Interpet's Liquisil General Tonic No. 5) can either be used once a month to reduce disease organism levels, so swinging the balance in favour of the fish, or used at times of particular stress, e.g. when poor water quality is identified, or new fish are introduced.

Vigilance

In spite of all precautions, disease episodes may still occur in the aquarium. It is critical to monitor your fish regularly so that you notice any abnormal behaviour or differences in appearance which may signify the onset of disease. Prompt and correct diagnosis and treatment is the secret to increasing the chance of success when treating fish diseases.