The aim of this paper is to examine case studies of production parameters and cost/income relationships of extensive pond fish systems. There is a global increase in demand for food, which presents huge challenges for terrestrial and aquatic food production to ensure sustainability. With the rise of aquaculture, fish meal – free, cereal-based carp production is becoming increasingly valuable from the perspective of sustainability. In addition, based on its production volume, cereal-based carp production is the third most significant fish species in global terms, while carp is also dominant among fish species in Hungarian pond systems. Data collected during the analysis were processed using descriptive statistical methods. To analyse the efficiency of production, changes in income were examined using different combinations of production parameters and certain cost items (ceteris paribus). Based on the obtained results, it can be stated that, in the case of the modelled farm, a 0.56 thousand € per hectare income can be realised. The initial cost and average weight at the moment of sales can greatly influence the profitability of a farm.