Public financial aid is approached as one of the most important tools allowing, mainly small and medium-sized enterprises, to implement many of their investment intentions, thus improving their competitive position in the market. It is granted to enterprises regardless of whether they are of profit-oriented or a non-profit nature. The main goal of this article is to assess the effectiveness of public aid in the aquaculture sector. Authors reviewed the aid measures allocated to three carp farms located in the Barycz Valley, the biggest center for carp breeding in Europe. These three farms accounted for half of the aid beneficiaries over the period of analysis, and are considered to be representative according to the typical farms approach. They also account for 85% of the total grants allocated to the sector. After identifying differences in investment strategies, the authors investigated whether these differences could be reflected in the financial situation of the selected enterprises. The analysis covered the value of the financial liquidity factors, profitability, the level of debt and the increase in assets during the years 2012–2016. The research suggests that part of the benefits expected from public aid are not fully captured in the traditional performance ratios, especially when ecosystem-enhancing measures are involved.