Over the years of serving the fish farming industry I have observed that owners become desperate, willing to go to great lengths, and expense, when their fish become sick.  The financial loss associated with fish dying is one driver of this frantic behaviour, but the emotional pain is usually an even greater force motivating people to do whatever they can to limit the loss.  In almost every instance the poor health is entirely avoidable through good planning and disciplined management of the culture environment.
 
There are many factors that can cause the health of our fish to be compromised, but the most important by far are water quality, feed quality and quarantining.
 
If the quality of the water in which the fish live is compromised in some way making it unsuitable for them, they do not have the option of leaving and going somewhere else.  Thus, it is up to us as fish farmers to ensure that the water quality always remains suitable for the species of fish that we farm.  Some of these parameters need to be measured more frequently than others, depending on the species of fish, the age of the fish and the type of infrastructure we are using.  To some degree the source-water quality also impacts testing frequencies.  By monitoring these parameters at appropriate intervals and applying remedial action early on, we can maintain water of an acceptable quality at all times, ensuring that poor water quality does not impact on the health of our fish negatively.
 
Feed is the source of all the building blocks, energy and essential micro-nutrients required by the fish.  If the feed lacks certain components, either in terms of quality or quantity, the result will ultimately be that the health of the fish will decline.  Ensure that you always feed the fish feed that is appropriate for the species and age of fish that you are farming.
 
In this time of Covid and Lockdown we have become familiar with the concept of quarantine to reduce the risk of introducing pathogens.  Fish farmers have applied this principle for decades by quarantining new stock for a period of 2-3 weeks to identify and eliminate any parasites or pathogens that the new fish may carry prior to them being introduced to the tank with existing fish.  A thorough microscopic assessment of the fish is needed prior to introduction and in some instances prophylactic treatment is also applied.  If new water coming into the systems comes from a source containing fish this water should be sterilised prior to use.
 
Applying these 3 management practices will go a long way towards reducing the risk of poor fish health.  Be sure that you have the microscope, dissection kit, test kits and meters necessary to conduct these tests.  In this way you will avoid the frantic panic of trying to solve a problem that should never have occurred.