A quick guide to fish health

Fish Health The Causes and Symptoms of Disease

Healthy fish have an efficient immune system that will attack pathogens that try to attack them but stressed or unhealthy fish will not have the same level of resistance against disease or infection.

It is highly recommended that when introducing new fish to a community tank they be quarantined in a separate cycled tank for at least two weeks prior. This way you are not immediately introducing new pathogens into your healthy aquarium or the new fish to new pathogens already present in your aquarium. It gives the new fish time to acclimatise and recover from the stress of being transported and placed in a new environment and gives the fish keeper time to observe and identify any disease outbreaks that may require treatment.

The pathogens, bacteria and fungal spores are present in every aquarium and the fish themselves carry their own bacteria, the pathogens can also be present in plants, live food or the equipment used and the furnishings or decorations in the aquarium, it only becomes a problem when the balance is upset. The main factor in fish disease is stress, it  reduces the efficiency of their immune system making an outbreak of disease far more likely.

The most common cause of this stress is poor water conditions, not cycling a tank properly or not doing regular partial water changes can have a huge impact on the water quality. Another cause is  fish bullying, it is always wise to check the compatibility of your fish before you introduce a new species but even if they are compatible it can still occur as a result of overcrowding so making sure your tank size is adequate for the volume of fish you have can help reduce occurrences of bullying. Capture or changing the environment of a fish can also cause it undue stress so the new environment should contain plenty of hiding spaces for the weakened fish to hide in and acclimatize. Finally poor nutrition can cause unwanted stress, care should be taken not to overfeed as it will pollute the water and harmful toxins will build up affecting the water quality but the fish should be fed a varied diet as much as possible suited to their individual needs on a regular basis. It is usually recommended small amounts twice a day. If your fish are breeding they will require a slightly larger amount. Fry may require small amounts up to four times a day.

Different species of fish will require different levels in water hardness this is usually measured in dH (degree of hardness) and varies depending on the amount of dissolved calcium carbonate present. Livebearers for example like hard water this is water ranging  from above 8dH that is slightly more alkaline whereas Tetras prefer soft acidic water with a range below this and ideally very soft below 4dH. It becomes more crucial when trying to breed the fish. For example it has been discovered that female Tetras kept in water with a level of 8dH will be incapable of breeding as their ovaries will become deformed.

The crucial factor in dealing with disease, infection and controlling it is constant observation, there are many symptoms to look out for and the behaviour of a fish will change if they become less healthy, they will exhibit early warning signs. If these are observed and diagnosed correctly early enough, it may be possible to treat the disease effectively and nurse the fish back to health. Sadly not all diseases are curable once they take hold. Some diseases are highly contagious and it may be necessary to treat all your fish and all your tanks whereas some will only be present in the sick fish. It is good practice to quarantine sick fish in a separate tank whilst you identify the cause in order to minimise the risk of infection spreading to the rest of their tank mates. There are many different available treatments for a variety of different diseases but prevention is always better than cure so maintaining a healthy environment for your fish, avoiding overcrowding and regular feeding will often ensure you have healthy fish that rarely suffer from disease.

In all honesty my fish haven’t suffered diseases very often, despite an outbreak of White spot and the odd unexplained death I have very little experience in diagnosing or treating disease but I am vigilant about their care and will quarantine fish that appear to be stressed. It is possible the high mortality rate in my Neon Tetras was down to an incurable disease combined with stress induced by capture and transportation. They do not seem as healthy or hardy as some suppliers may lead you to believe.

Below is a chart of symptoms and diseases to look out for but please remember that the behaviour of a fish will change for natural reasons too, such as breeding, spawning, birthing or simply stress. This is just a rough guide of the diseases that can be treated and their definite symptoms. The following information is sourced from Interpret who also produce a range of treatments for aquariums.


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