In commercial fish farming units you can look at various biochemical and morphological markers for a greater understanding of health and disease status of the unit. Aim of a study was to examine some biochemical metabolic indicators in some common diseases in farm carp. Especially levels of ammonia in branchionecrosis (BN). The research was done in 2009–2011 and 120 carp of 25–90 g less than one year old were sampled for the following diseases: spring viraemia of carp SVC and CE, swim bladder infection, branchionecrosis and also any appearance of transsudative changes in fish with no clinical signs. The research was done in the Lower Silesia region. These indicators can be useful in determining the health of the fish and possible causes of an illness. Electrolytes, protein assays and hematology are useful in diagnosis in carp disease thus enabling more effective treatment. Low sodium levels in particular are a useful predictor of a disease.

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