The College of Education – Al-Qurna at the University of Basrah discussed a Master's thesis in the Department of Biology by student Aya Sabah Al-Subeih titled The Effect of Substituting Different Proportions of Azolla in Diets on Some Morphological and Histochemical Characteristics of Grass Carp. The study aimed to determine the impact of plant substitution on various growth parameters such as total weight gain, relative growth rate, daily growth rate, specific growth rate, and food conversion ratio.

The research included a histochemical aspect that involved observing histological changes in the gills and muscles of the anterior (R1) and posterior (R2) regions, as well as calculating the numbers and diameters of red and white muscle fibers in both studied areas. Furthermore, the study estimated the protein concentration in muscle fibers using the BCA assay method and determined the percentages of amino acids and fatty acids in the targeted regions.

The study concluded that a 15% substitution rate of Azolla was superior as it achieved the highest levels of protein, amino acids, and fatty acids. These results indicate the possibility of using Azolla as a sustainable and low-cost nutritional component in aquaculture systems, which reflects positively on the economic aspect.