Aquarium fish are becoming more and more popular as pets.  Once a tank is established they are a low maintenance option which can provide endless entertainment.  Aesthetically a well designed tank can create a stunning focal point in a room. Both freshwater and marine tropical tanks are gaining popularity.  We would recommend to anyone entering the fish hobby to start with freshwater fish.  Marine tanks, although spectacular, are far more demanding in terms of both time and money.

Just like other pets, fish are susceptible to a variety of parasites and diseases.  Most health problems are directly related to the quality of the water the fish are kept in.

WATER QUALITY

A fish tank is effectively a closed ecosystem.  Any waste products produced by the fish or uneaten food needs to be broken down by an effective filtration system.  Filters may include mechanical, biological and chemical components.  Fish produce ammonia, excreted via the kidneys and gills.  Ammonia is toxic in high levels.  The higher the water temperature or pH (more alkaline) the more toxic the ammonia becomes.  In a functional biological filter the ammonia is rapidly broken down into nitrite (very toxic) and then into nitrate (far less toxic) by bacteria.  Nitrates can be used by plants in the tank, so theoretically a stable safe environment can be maintained.  A partial water change of around ten percent is recommended weekly.

Most disasters with fish tanks are seen during the first few months after set-up.  The typical scenario is where a new tank is purchased, filled and fully stocked with fish straight away.  Inevitably the system crashes within a few weeks with the loss of fish and sometimes the owner's enthusiasm!  A new tank should ideally be filled and left for at least a week.  This allows an opportunity for the water temperature to be set at the required level and where tap water is used, allows any dissolved chlorine or nitrogen to dissipate.  Rain water is always a better option than tap water if available.  Ideally the filter should have a component containing filter charcoal to remove any potentially toxic chemicals. 

A few small fish can be added at this stage.  Limit feeding to a minimum, all food should be consumed within a few minutes.  Uneaten food is a major source of ammonia!  Regular partial water changes should be made during the set up stage.  Once the system is stable, typically around six to eight weeks, further fish can be added incrementally until the tank is fully stocked. Ideally, water quality parameters including temperature, pH and ammonia levels should be regularly monitored during the first few months.

As poikilothermic (cold-blooded) animals, fish do not tolerate rapid changes in water temperature.  When new fish are purchased it is important to float the bag containing the fish in the tank for at least fifteen minutes to allow the water temperatures to equilibrate prior to releasing them.

DISEASES AND PARASITES

There are a number of common diseases that affect fish.  Typically disease outbreaks can be related either to newly introduced fish infecting the tank, or to less than optimal water quality conditions affecting the fish's immune system.

Probably the most frequently encountered is "White spot" a protozoal parasite, Ichthyophthyrius multifiliis, that can rapidly decimate a susceptible fish population.

Gyrodactylus and Dactylogyrus are skin and gill flukes that are common in both tropical and temperate water fish species. These are microscopic worms that attach to the gills or skin of the fish and can be rapidly fatal particularly in some species such as Discus.

For information on the diagnosis and treatment of fish diseases please contact us.

AQUACULTURE

Fore those breeding or keeping fish on a larger or commercial scale the challenges and complexity of fish keeping increase dramatically.  Water quality is still the major factor in maintaining health and growth but nutrition becomes more critical.  Depending on the species of fish involved, live food such as brine shrimp (Artemia) may need to be cultured, creating a whole new set of challenges.

One of our vets Dave Kruger has a post graduate degree in Aquaculture (MSc) and maintains a keen interest in all things piscine!  Please feel free to contact us for advice or information in this field.